@@woodshopnerdery I am sure it does. Current family and financial situations are prohibitive at the moment. Maybe that will change. Keep up the good work! I need sawdust time
Thanks for all the insight here! Well put together. I run a similar size dust collector, but I split the 4" into two 2.5" lines. It's not optimal, but it does help, vs reducing it to one 2.5" line out to the machines. I have three machines connected to it, but use blast gates, and always have two of them open. I did a series of redneck experiments and have found a sweet spot for my configuration. Distance of hose makes a pretty big difference too.
Thanks for the compliment! Can't take credit for the idea to use the Pitot tube. I read that it is the way Oneida Air tests their gear and I saw it used in several other dust collection materials. Just a copy cat!
Great video, thanks for sending the link. I have never measured the air quality in my shop, so the particle counts leave me with more questions than answers. I was surprised at the spike just from walking around, but I couldn't quite tell from the video if your concrete floor is unfinished. Also, if you clean the floor with a broom, more dust would remain than if you clean with the dust collector and a wide brush attachment. I might have to pick up one of those meters to do a comparison. As for the filtration levels, I think that my Wynn Environmental filter was advertised as a 0.5 micron when I bought it (they use MERV ratings now), which was a big improvement from the 5.0 micron that came with the Harbor Freight dust collector. I could taste the dust in the air when I was using the HF bag, but with the Wynn filter, I have only even noticed a strong wood smell when cutting Meranti - The air stunk for days every time I turned on the dust collector until I blew out the filter and changed the plastic bag. It makes me wonder what the average size of a sawdust particle is, from sanding, power-planing, table-sawing, etc. Continuing with that last thought, the size of particle blocked by a filter will decrease with time until the filter becomes completely clogged. Even when you shake or blow out a filter, there will still remain small dust particles clogging the larger holes. A 2.5 micron filter will eventually become a 0.1 micron filter if it gets dirty enough. A thorough bag cleaning, maybe using compressed air or shaking it out, might restore the filter closer to its original specs, and might increase the
Thanks for the compliments. Glad you liked the video. I think its a common misconception that a 2.5 micron rating means that ALL particles larger than 2.5 microns are trapped and ALL particles under that size pass through. This is not really the case. The rating means that the filter material will trap 95% (I think) of the particles 2.5 microns or bigger at a certain air velocity. The filter still traps lower sized particles but just not 95% (or whatever %) of them. Maybe it traps 70% of sub-2.5 micron particles for example, just a guess? I believe you are correct, the dust cake on my bag does increase it's particle efficiency. But, my collector is also under powered at 1 hp. It produces no where near the air velocities used to do the particle filtration ratings tests. So, my assumption, is that if the air is moving slower, it pushes fewer particles, of all sizes, through the filter material. So, at my system's air velocities, I wonder if it is behaving similar to a 1 micron filter on a larger more powerful system? wynnenv.com/woodworking-filters/filter-efficiency/ BTW - I think you have a great set up. I would go that direction with mine, but I just think the motor on mine is too weak to support the upgrades. What I will probably do eventually, is go with a premade system like the Oneida Mini Gorilla.
Thanks for the video. I just got my dust collection going and was planning on “upgrading” to a canister filter. Other UA-cam videos make it sound like you will develop some sort of lung disease if you run the cloth filter. Appreciate you taking the time and showing us that it’s not as bad as some make it sound. I do understand that the canister filter would help, but I’m not in such a hurry to get that done. Thanks again. Great job!
Thanks Troy, glad you liked the video. I'm in the same boat as you, I have seen all those YT videos and almost got the point of feeling guilty about it. So I just broke down to 2 questions, "What problems do Canisters solve?" and "Do I have those problems?" I guess a follow up questions is, "Is there a cheaper way to solve those problems?" For example, maybe buy a better bag?
I completely agree with you on the subject of filter bag vs canister filter. I'm sure the canister filters work great. But... -Both pleated filters and filter bags have to be cleaned. Neither can be washed, but filter bags aren't difficult to clean. -A canister filter doesn't seem as easy to clean, and I doubt they can be cleaned as well as a filter bag can be cleaned. I would think there would always be some dust trapped in the pleats that would never come out. Which means no matter how well you clean the canister filter, your dust collector's cfm's would slowly decrease over time with a canister filter; more so than a filter bag. -Also at some point a canister filter or a filter bag will have to be replaced. I'd prefer to spend a lot less money on a filter bag than a canister filter. In fact, you could buy a few filter bags for the same cost as one canister filter to keep in stock, and the bags take up a lot less room. -Plus, the risk of a big canister filter getting damaged just from storing is a lot higher than filter bags. I'd say there are more pros for filter bags, and more cons for canister filters.
Chad, very good points. I could see the argument for a canister filter(s) in a multi person shop where multiple professional grade machines are running. And there could be other places where canisiter filters are ideal. But, for one man shops and certainly for hobbyist I think all of you points are SPOT ON!
@@rfguy8499 I watch Stumpy Nubs (James Hamilton) as well. As I'm sure you're aware, he's put out quite a few videos on the subject of dust collection and filters over the years. So yes, I'm aware of what cyclones do, and how to clean HEPA filters also. According to Stumpy; never wash a filter hood. Washing removes the coating on the fabric that filters the fine dust and lets it back out into the air. I agree with that statement. If you or anyone else use a filter hood, and have been washing it, then I recommend you replace it asap.
@@woodshopnerdery Hey, at least you use dust collection in the first place. I've helped certain friends over the years that didn't use any dust collection at all. Just a push broom and a dust pan at the end of the day was all they believed in. And in the winter with their garage doors closed to hold the heat in; they'd have a haze of fine dust in the air for several minutes or longer while sanding or running a table saw, just breathing all that in. No thank you.
@@chadnevels246 It's better to do something than nothing. I feel pretty good about what I have, but still have an eye out for reasonable improvements. For example, Rockler has a "Shaker Felt" bag for $40 I might try out. It's rated at 1 micron and has a lot more sqft of filtration than the one I have. Might be worth trying at that price.
@@rfguy8499 We are certainly flooded with information that does not always agree. It's hard to no how to reconcile the discrepancies, which is why I like to do a little proof of concept if I can. BTW - I think Chad could be saying he watches Stumpy Numbs as well as my channel. But, it could be taken either way.
Totally agree Coppertune. I wish I had a way to distinguish among "environmental" particles and wood dust particles. I guess the best I can do is try to establish a base-line of background particle counts.
Damn, wish I knew this two years ago before I sprung for a canister filter! 😣 For overall air filtration I just use two 20” box fans hung from the ceiling of my shop like yours. Izzy Swan found that they work as well if not better than the expensive types. Good quality furnace filters work great!
Thanks for watching and commenting! I love to see the comments. I saw the Izzy Swan video about the box fan filter too, but I wasn't convinced until I saw this video ua-cam.com/video/kH5APw_SLUU/v-deo.html I'm sure your canister upgrade was a smart move for your system. Believe me, if the sensor showed high particle counts in my garage I would have immediately ordered a canister. I hope the take-away people get is that each system is different and there is no one size fits all solution.
On a cost analyse basis the pleated filter canisters seem to come out on the short end of the stick. In terms of lifespan the paper elements are going up in price with that limited useful life while the felt seems to be a very long term purchase that is easily recleanable. Going with your figures and some others it would appear that felt is the best choice. Since my shop is a combination wood and metal I would be very interested in metal central collection of the swarf and if it is possible or practicable.
Great points Douglas. I since posting this I upgraded to a 42 inch 1 micron felt filter. Was $40 from Rockler. Has great air flow and great filtration and was many times less expensive than a canister.
Great follow-up video. I have done similar tests in my own shop before. Sometimes outdoors is significantly less than my shop and sometimes the opposite. Outdoor particulate levels vary a lot depending on weather, local pollution levels, landscapers running leafblowers, neighbor's diesel pickup, etc., etc. IF you live in a city with high pollution then I would expect outdoor particulate levels to be worse than your shop, but that isn't really a good argument for why you don't need a HEPA cartridge filter on your DC in your shop IMHO. Bottomline is that around 0.3um particulate levels are just hard to filter due to Brownian Motion causing degraded filter efficiency in this range. A bag filter is just much less efficient at capturing particles around 0.3um than a HEPA cartridge is, but whether or not you want to pay for a better filter is totally subjective. I just wouldn't use outdoor air particulate levels as my baseline...I strive to have my shop, and house, be much, much cleaner than outdoors because this is where I spend most of my time so it has the most affect on my health. With proper filtration, IAQ should be far cleaner than outdoor air in most locales.
RF Guy - Thanks for the comments. I'm curious if outdoor air is not a good baseline, then what is a good baseline? Also, what are your particle counts running your cyclone/HEPA canister system? BTW - www.airnow.gov/ - On the day of the test, my area (and most of the country) was at PM2.5 70 Moderate. Today it is PM2.5 28 Good for my area and most of the country. EPA has long recommend ventilating outside air as a major strategy for improving indoor air quality. www.epa.gov/indoor-air-quality-iaq/improving-indoor-air-quality
@@woodshopnerdery For a baseline, you could target the green range in the AQI recommendations from the EPA, but I don't even think the EPA specifies or measures particle counts below PM2.5 unfortunately. My approach is as follows: I run my air cleaner in my shop when it is not in use, so when I enter my shop to work, I use this level as my "baseline". I mainly focus on the 0.5μm range on my Dylos which is typically around 200 or less. Then as I am working, I just keep an eye on the Dylos. Usually it stays under 400 for most operations, but for certain sanding operations it can climb above this. Whenever the counts get above 1000 (like some sanding operations), I take a break from my shop and come back a short while later to resume work. I am not saying everyone should do this, but this is just my method. This works for me with the Dylos because each reading is averaged over 10 samples. It is much harder to implement this method with meters that are instantaneous reading only because it fluctuates so much reading-to-reading. Bottomline is I try to keep my shop close to the particle count levels that I maintain inside my home. I also run air filters in my house so my IAQ is better than the average home. The EPA ventilate to outside rule only really works when the outside air is cleaner than inside right, but what if you live in a big city? Ventilating to the outside means also pulling in outside air to replace it to maintain pressure inside the house. IF you live in a very polluted area it may be inadvisable to ventilate outside because you'll pull in much more polluted air from outside to replace it...
Great method. And a good set of goals. I think I have been doing something analogous, but maybe not as rigorous and with somewhat more relaxed goals. I look mostly at the AQI screen because I can see it across the garage, it shows a single value in large font. It normally stays in the "Good" range but during some operations spikes into the "Moderate" range but is within minutes cleaned back up to "Good". And boy if I forget to turn on that dust collector, then numbers go way up, and yes I do turn on both my systems and come back in 10-20 minutes. I know the AQI is not a perfect measurement. I like your 0.5 micron approach. But like you said, on my unit the detail screen shows instantaneous measures, so it can be quite "peaky". That is why I showed the min and max values in my video. But on my unit I believe the AQI "estimate" is calculated over several sample reading across all practical sizes. Not the 24 hour period spec'ed out by the AQI standard by it is a "rolling average" of some sort. So I try to keep it in the "green" and also look at the trend up or down and try to make sure it trends downward between operations. If money were no object I would go with the Oneida Mini-Gorilla. It seems like it would meet my needs while still fitting in my limited space. I think that sort of upgrade is what it would take to get an appreciable change over what I have now. I think if I simply swapped my felt for pleats it would not be a game changer.
@@woodshopnerdery Yeah, I think you are on the right track with all of this. I am not saying my method is the only way to do it. I mainly just wanted to highlight that outdoor air quality can be crap in some areas so I wouldn't use that as a baseline. I am also a strong advocate for HEPA cartridge filters, but I know they come at a cost and may not be suitable for everyone. I really wouldn't recommend anyone switch to HEPA cartridge filters unless they can afford the airflow drop with putting a cyclone in front of the DC first. Otherwise as soon as the cartridge filter clogs up, their airflow will drop precipitously which will compromise dust capture at the tool resulting in even more dust particulate entering the shop atmosphere. For me, I try to keep my shop as clean as possible...hopefully close to my indoor AQI levels. My shop is in an attached garage so entering/exiting the shop allows some of that air to interchange and I really don't want any of that dust getting into my living space. As a result, I may be more rigorous with my approach to all of this, but for good reason. With regard to instantaneous readings on particle counters, I have been meaning to try to hookup one of those PlanTower sensors to a laptop so that I could do my own averaging and data display. It would definitely be more useful with a running average and histogram display to see how different shop operations affect shop air quality.
Another suggestion is to measure with and without bag on your dust collector. And compare the numbers with and without the reducer. I would also suggest that you use a y fitting to split the 4 inch and use one on the dust port and another as an auxiliary port near to not big down your dust collector.
Aravindah, thanks for the suggestions. I totally agree with you. I did do what Oneida Air calls, "Free Fan" testing with an Anemometer in my first video on my dust collector. I found that the coupler/reducer is by far the biggest bottleneck in the system and concluded that getting a canister filter is not guaranteed to improve the air flow. Here is the video if you are interested - ua-cam.com/video/IeXHpUmrNVM/v-deo.html Also, great call on the splitter. To avoid buying a second machine to collect dust from my orbital palm sander, I use this same dust collector. But, I add a 4 inch to 2.5 inch Y adapter to allow "make-up air" to flow into the 2nd port since the sander is very restrictive on air flow. The purpose, as you say, is to avoid bogging down and stressing the motor. But it has to be in balance, I find that I must block about 60% of the open Y port to maintain sufficient air flow through the sander.
Tend to think that the kind of material you typically work with (species of wood in this case) and your reaction to that wood and its dust is the bigger issue. Most wood dust is very irritating to lungs but for some extremely more so. In those situations a "better" or finer filter is pretty much a given if you plan to continue in the hobby. Obviously other factors like exposure time, duration, and machinery used are all pieces of information for the health puzzle. Clearly a hand plane has less of an impact to dust creation that a 3-HP router. Or compare impact of working Cocobolo or Rosewood to Alder or Birch. Hardwoods versus man-made composites like MDF. Base line is if you aren't cleaning your nose regularly or often then you mIght be OK but be cautious as your activity ramps up.
Thanks Don. I totally agree that wood dust and especially fine wood dust is a serious hazard. I did purchase a 42 Inch 1 micron bag from Rockler for $40 since making that video and it's working well.
Thanks, I really enjoy this kind of inquiry in addition to making projects. I'm trying to keep a balance of both types of videos. Yes, I have looked into the Thein baffle, bucket separators, and cyclones. Although the mechanisms are different they all employ gravity to separate heavier materials from lighter BEFORE the fan. They also lower the CFM quite a bit initially but help maintain CFM by preventing the filter from clogging. This is good for shop vacs because once the filter is clogged the CFM goes to almost zero anyway and the filter is a total pain to clean. To start I had a tool box style Rigid vacuum, then I added a Dust Deputy, which kept the filter clean and the vacuum running at peak (~80 CFM maybe?). But it was irritating to move around and always fell over. I looked into building a cart but realized that if I was going to dedicate floor space to a cart I might as well invest in a proper dust collector. So I purchased the unit I have now, it was an amazing difference in air quality, cleanliness and generally enjoying my time in the shop more. In my opinion I would not benefit from a pre-fan chip separator like a Thein baffle; 1. I have a metal fan so no need to protect it from chips, 2. it's a small system so I don't have extra CFM to spare, 3. my felt bag can be cleaned with a few taps to restore optimal CFM so no need to protect the filter from clogging. 4. true bag-bottom, filter top dust collectors like mine already separate materials using gravity. The one exception is on some rare occasions when I use the planer and jointer I do get a clog at the inlet of the dust collector motor housing. In this case I could benefit from a pre-separator. But, to clear it out takes 1 minute and I don't want to store a separator when I only need it 1% of the time. Hmm... now I'm thinking... When I got my dust collector I gave my Dust Deputy to a co-worker for his garage shop. They work wonders for shop vacs, but for my system it would eat away my CFM because they do that and because it would require I use a 2.5 inch hose instead of a 4 inch hose which also is a CFM killer. There you go some bedtime reading😴😴😴😴😴😴😴
@@woodshopnerdery The original Thein baffle wasn’t pre-fan and was actually designed to be installed inside a dust collector like yours. I agree with your assessment or the pre-fan separators.
I had not heard of an internal Thein baffle. But I looked it up and learned we are spelling it WRONG, should be Thien. Anyway, no I don't have one. Is the purpose to prevent the inlet air from stirring up old dust in the lower bag? Have you added one to your dust collector? Is it having an impact?
@@woodshopnerdery Ok, so it looks like you've learned the first lesson, and that's you should never look to me for proper spelling! I used to say that I spell atrociously, but then my bride pointed out that no, I can't! Anyway, no, the point is to get the dust to drop out of the air before it hits the filter. It's not unlike the cyclone that is already designed into your separator but even more effective. I have a SS DC3300, so I can't install one, but I may buy another, larger DC and if I do I'll install one in it. Scott
@@MyGrowthRings I'll have to put some thought into it. I guess it's suppose to give the dust a longer arc of travel in a slower air stream so it can drop out? Interesting.
I purchased the SSmith upgrade DC motor. The amount of air moved by the new motor is significant. I removed the 3 way intake on the DC 3300 and in its place installed a 4” connector. As well I ordered and am using a 4” hose from the DC to the Smith. I purchased a 4” to 2-1/4 reducer, clamped about 12” of 2-1/4” length of hose enough to move the table or headstock without interference. The lack of sawdust, bandsaw dust, improvement of conical disk dust is - well I’m glad I purchased the new motor, connectors and hose. Ok - but!! It’s foolish to argue against data I know but - are you sure you didn’t confuse the two data sets?
Hi John, thanks for questions. I don't read too much into the data. Its just engineering field measurements and NOT a lab setting scientific study. I think of it as akin to reading my own body temp as a diagnosis for an illness. I was simply "taking the temperature" of my dust collector to see if I could find any common "illnesses." I don't see any right now. I think you have a great setup with the DC6000. And running the 4 inch hose as long as possible before reducing to 2.5 inch removes A LOT of friction from the system which avoids major drops in CFM.
I don't think I confused the data sets because I watched the video several times while editing and you can see right within the footage some of the numbers at each location. All the outside measurements prove to me is that my device is capable of reading higher values.
@@woodshopnerdery I too watched and confirmed exactly what the data shows. However - that said…. you are in a confined space. Dust is being generated. The dust can go into the collector and some of it won’t. The hood too is “open” enough that …. I don’t get it - I’ll be …….!👍👍 And I’ll say again the audio and video quality is most excellent. Nicely done.👍👍
Thanks for the compliments. I've been trying to get the best audio and video I can with the equipment I have, iPhone, cheapo camcorder, computer mic. I wish it were better, but this is just a hobby for me so... I used Shotcut to put it together which is a very basic free application. Don't get me wrong, I am concerned about the dust. I know very well that broadly speaking 50% of the dust is not collected immediately. This is why I have the ambient filter. But, there is only so much a dust collector can do. I have adequate CFM and my filter is capturing particles of all sizes. So it is helping. Could I invest $1500 and do better, of course I could. But when is good enough, good enough? I'm still trying to discover these answers. I think that there is a popular misconception with filters that it either gets 95% of 0.3um particle or it gets NOTHING and lets EVERYTHING through. That is not true as far as I can tell. My filter is still getting the particles, but instead of 95% efficiency perhaps as a best guestimate maybe only captures 80% of 0.3um. So if I cycle the air twice through my system does the filter get 96% (80% + (20% x 80%))? I think my test showed some indication of that, the longer it ran the more the particle counts dropped.
I would have bought a Shopsmith DC but at the time the DC-330L was out. That looked to me like a Rikon 60-100 with Shopsmith labels on it. So that is why I looked off brand. Glad I did. This Shop Fox is a great value. I may upgrade to something else one day, but its working great for now.
Really like the data! Thanks. Do you have a link to the particle counter in this video? It seems like everyone who is doing a video with CFM measurement should always do one reference point at the entrance to the dust collector. Variations after that are infinite.
The particle meter is a cheapie from eBay. I can’t give a link because the listing changes every few weeks. That one has since stopped working and I purchased a Dylos brand unit. I did use a anemometer in the first video to measure the intake. The method I used in this video is inspired by Oneida’s real world testing methods, which involves a pitiful tube at the end of a 10 foot hose. That would be the minimum resistance any system would have but still is plausibly usable.
another awesome video! agree the canister setup may not really provide much more protection But here is the thing, don't put all your donuts in the air filtration alone USE a good quality N95 or similar face mask when cutting, sanding, grinding, spraying in an enclosed space with poor outside air circulation! Oh and another thing, Great Scott! if DOC Brown had you as an assistant who knows perhaps the "BTTF" Time Machine could've been a Ford Mustang instead of a DeLorean! Wait a minute, you didn't use this whole nerdery experiment to build your own time machine so that you could back into the future and kiss an 18 year old version of your mother? {okay probably not very appropriate comment but it did happen in the movie, so just saying!}. all seriousness, this one video probably solidifies your spot in the Nerdery video Hall of Fame, truthfully it is that good. thanks for sharing.
Thanks for the compliments! And thanks for the nudge on the dusk mask. I worked myself into a really good habit of wearing either an N95 or a Respirator. But got out of that habit in 2020 when I could not buy replacements. But the N95s are on the shelves again and I NEED to get back into that routine.
Very helpful - thanks. I have the same dust collector ( bought only craiglist brand new before seeing this video ) and also 2 1/2 inch at tools (shopsmith) . I tried your set up and I am now experimenting with a y at dust collector 4 inch to pair 2 1/2 outlets and using 2 1/2 hose to one tool and other outlet open or 2 hoses to 2 machines. It seems to work better than 4 in hose with reducer - I have tapered reducer similar to yours. I can not do any measurements though. What do you think ? I also have cloth filter and had canister envy but no more - thanks - money for some other toy.
John, I did do some testing for the first dust collector video on my 2.5 inch hose. I did not include it in the video because honestly I did not consider it a viable option. I put the reducer directly on the DC and then ran a 10 foot 2.5 inch hose. Note my 4 inch hose is also 10 foot. At the end of the 2.5 inch hose I measured 87 less CFM than I measured at the end of my 4 inch hose with the 4 to 2.5 reducer. The measurement I got for the 2.5 inch hose was 110 CFM, which is about the same as Shop Vac. Friction between the air and the side wall is the enemy. Larger diameter hoses have a greater cross section area per linear unit of circumference than the smaller diameter hoses. In other words, larger hoses have less friction per volume. The conventional suggestion, which I see all over the place, is to run the largest diameter hose or pipe possible until the last possible place, then reduce to smaller. Keep in mind that with a DC you want high air volume movement. The air may have a higher linear foot per minute rate at the end of a 2.5 inch hose, so to the eye and hand it looks and feels like better performance because the air is moving faster. But the goal is to get better air volume movement, while still maintaining a minimum of about 4000 feet per minute flow rate. Common wisdom is that air moving at 4000 fpm keeps the particles suspended in air so they can be collected.
Doesn't really ADDRESS the question posed in the title of the video. You're just making an assumption based on data collected ONLY from a bag filter. You really need to buy a HEPA or 1micron canister filter & compare the numbers to the bag filter results in order to address the question.... Canister filters DO improve airflow, which even with 2.5" reducers should show a measurable difference. The real question is how much improvement is there in changing from a bag filter to a canister filter.
No it did address the question. There would be little to no improvement on my machine. Look at the "free fan" measurements without any filter vs the "clean bag" measurements. There is only a 5 cfm difference. So assuming these expensive canisters have 0 air flow resistance (with is impossible) I would only get 5 addition cfm out of it. And as the difficult to clean pleated filter became impacted with dust the cfm would drop significantly well below the bag filter. Canisters manufactures should list the cfm per square foot of material and the total square footage. BTW after this video I bought a 42 inch 1 micron bag filter from Rockler rated at 50 cfm per square foot. It was only $40 and supports more than enough total air flow for the capabilities of my machine.
that AirNow ppm meter detector is the weak point in your analysis. It is an inaccurate and unreliable device to base your assumptions and conclusions on.
Please check my Community tab for answers to common questions and the latest information! - ua-cam.com/users/woodshopnerderycommunity
Thanks for the data driven analysis.
You’re welcome,Don.
In both of your dust collector videos you make one valuable point: clean out the bag! How right you are.
Good catch. I was hoping people would pickup on that.
Thomas, thank you, as always! I’m still with a shop vac and respirator …
Thanks for watching John!
Once again you are killing me! I like my shop vac but now thinking maybe...
Thanks for the compliments. I definitely don't regret moving up to a dust collector from a shopvac. The higher CFM makes a huge difference.
@@woodshopnerdery I am sure it does. Current family and financial situations are prohibitive at the moment. Maybe that will change. Keep up the good work! I need sawdust time
@@Me58651 I hear you on the financial priorities. It's just at hobby after all, lots of other demands on our time and financial resources.
Love that you always think these videos through. Another great video.
Thanks! Glad you enjoyed the video. I really like inquiries like this, I didn't see enough on UA-cam so I started making my own!
Thanks for all the insight here! Well put together. I run a similar size dust collector, but I split the 4" into two 2.5" lines. It's not optimal, but it does help, vs reducing it to one 2.5" line out to the machines. I have three machines connected to it, but use blast gates, and always have two of them open. I did a series of redneck experiments and have found a sweet spot for my configuration. Distance of hose makes a pretty big difference too.
Thanks for the compliment and comment Denny. I use your same approach in that you have to do the best you can with what you have.
Good job man. I wouldn’t have thought of using a Pitot tube for testing this, but it makes sense
Thanks for the compliment! Can't take credit for the idea to use the Pitot tube. I read that it is the way Oneida Air tests their gear and I saw it used in several other dust collection materials. Just a copy cat!
@@woodshopnerdery Plaigerism is the ultimate form of flattery. Not sure who said that, but I think it applies here.
I'm really diggin your channel. I appreciate your knowledge and ability to test these type of situations. Thank you for sharing.
Thanks Jim! Glad you liked it. Woodworking is a great outlet for us very curious types of people.
Great video, thanks for sending the link. I have never measured the air quality in my shop, so the particle counts leave me with more questions than answers. I was surprised at the spike just from walking around, but I couldn't quite tell from the video if your concrete floor is unfinished. Also, if you clean the floor with a broom, more dust would remain than if you clean with the dust collector and a wide brush attachment. I might have to pick up one of those meters to do a comparison.
As for the filtration levels, I think that my Wynn Environmental filter was advertised as a 0.5 micron when I bought it (they use MERV ratings now), which was a big improvement from the 5.0 micron that came with the Harbor Freight dust collector. I could taste the dust in the air when I was using the HF bag, but with the Wynn filter, I have only even noticed a strong wood smell when cutting Meranti - The air stunk for days every time I turned on the dust collector until I blew out the filter and changed the plastic bag. It makes me wonder what the average size of a sawdust particle is, from sanding, power-planing, table-sawing, etc.
Continuing with that last thought, the size of particle blocked by a filter will decrease with time until the filter becomes completely clogged. Even when you shake or blow out a filter, there will still remain small dust particles clogging the larger holes. A 2.5 micron filter will eventually become a 0.1 micron filter if it gets dirty enough. A thorough bag cleaning, maybe using compressed air or shaking it out, might restore the filter closer to its original specs, and might increase the
Thanks for the compliments. Glad you liked the video.
I think its a common misconception that a 2.5 micron rating means that ALL particles larger than 2.5 microns are trapped and ALL particles under that size pass through. This is not really the case. The rating means that the filter material will trap 95% (I think) of the particles 2.5 microns or bigger at a certain air velocity. The filter still traps lower sized particles but just not 95% (or whatever %) of them. Maybe it traps 70% of sub-2.5 micron particles for example, just a guess?
I believe you are correct, the dust cake on my bag does increase it's particle efficiency. But, my collector is also under powered at 1 hp. It produces no where near the air velocities used to do the particle filtration ratings tests. So, my assumption, is that if the air is moving slower, it pushes fewer particles, of all sizes, through the filter material. So, at my system's air velocities, I wonder if it is behaving similar to a 1 micron filter on a larger more powerful system?
wynnenv.com/woodworking-filters/filter-efficiency/
BTW - I think you have a great set up. I would go that direction with mine, but I just think the motor on mine is too weak to support the upgrades. What I will probably do eventually, is go with a premade system like the Oneida Mini Gorilla.
Thanks for the video. I just got my dust collection going and was planning on “upgrading” to a canister filter. Other UA-cam videos make it sound like you will develop some sort of lung disease if you run the cloth filter. Appreciate you taking the time and showing us that it’s not as bad as some make it sound. I do understand that the canister filter would help, but I’m not in such a hurry to get that done. Thanks again. Great job!
Thanks Troy, glad you liked the video. I'm in the same boat as you, I have seen all those YT videos and almost got the point of feeling guilty about it. So I just broke down to 2 questions, "What problems do Canisters solve?" and "Do I have those problems?" I guess a follow up questions is, "Is there a cheaper way to solve those problems?" For example, maybe buy a better bag?
I completely agree with you on the subject of filter bag vs canister filter. I'm sure the canister filters work great. But...
-Both pleated filters and filter bags have to be cleaned. Neither can be washed, but filter bags aren't difficult to clean.
-A canister filter doesn't seem as easy to clean, and I doubt they can be cleaned as well as a filter bag can be cleaned. I would think there would always be some dust trapped in the pleats that would never come out. Which means no matter how well you clean the canister filter, your dust collector's cfm's would slowly decrease over time with a canister filter; more so than a filter bag.
-Also at some point a canister filter or a filter bag will have to be replaced. I'd prefer to spend a lot less money on a filter bag than a canister filter. In fact, you could buy a few filter bags for the same cost as one canister filter to keep in stock, and the bags take up a lot less room.
-Plus, the risk of a big canister filter getting damaged just from storing is a lot higher than filter bags.
I'd say there are more pros for filter bags, and more cons for canister filters.
Chad, very good points. I could see the argument for a canister filter(s) in a multi person shop where multiple professional grade machines are running. And there could be other places where canisiter filters are ideal. But, for one man shops and certainly for hobbyist I think all of you points are SPOT ON!
@@rfguy8499 I watch Stumpy Nubs (James Hamilton) as well. As I'm sure you're aware, he's put out quite a few videos on the subject of dust collection and filters over the years. So yes, I'm aware of what cyclones do, and how to clean HEPA filters also. According to Stumpy; never wash a filter hood. Washing removes the coating on the fabric that filters the fine dust and lets it back out into the air. I agree with that statement. If you or anyone else use a filter hood, and have been washing it, then I recommend you replace it asap.
@@woodshopnerdery Hey, at least you use dust collection in the first place. I've helped certain friends over the years that didn't use any dust collection at all. Just a push broom and a dust pan at the end of the day was all they believed in. And in the winter with their garage doors closed to hold the heat in; they'd have a haze of fine dust in the air for several minutes or longer while sanding or running a table saw, just breathing all that in. No thank you.
@@chadnevels246 It's better to do something than nothing. I feel pretty good about what I have, but still have an eye out for reasonable improvements. For example, Rockler has a "Shaker Felt" bag for $40 I might try out. It's rated at 1 micron and has a lot more sqft of filtration than the one I have. Might be worth trying at that price.
@@rfguy8499 We are certainly flooded with information that does not always agree. It's hard to no how to reconcile the discrepancies, which is why I like to do a little proof of concept if I can.
BTW - I think Chad could be saying he watches Stumpy Numbs as well as my channel. But, it could be taken either way.
I think an important idea to consider is not only the number of particles present, but the type of particles present.
Totally agree Coppertune. I wish I had a way to distinguish among "environmental" particles and wood dust particles. I guess the best I can do is try to establish a base-line of background particle counts.
Damn, wish I knew this two years ago before I sprung for a canister filter! 😣 For overall air filtration I just use two 20” box fans hung from the ceiling of my shop like yours. Izzy Swan found that they work as well if not better than the expensive types. Good quality furnace filters work great!
Thanks for watching and commenting! I love to see the comments. I saw the Izzy Swan video about the box fan filter too, but I wasn't convinced until I saw this video ua-cam.com/video/kH5APw_SLUU/v-deo.html
I'm sure your canister upgrade was a smart move for your system. Believe me, if the sensor showed high particle counts in my garage I would have immediately ordered a canister.
I hope the take-away people get is that each system is different and there is no one size fits all solution.
On a cost analyse basis the pleated filter canisters seem to come out on the short end of the stick. In terms of lifespan the paper elements are going up in price with that limited useful life while the felt seems to be a very long term purchase that is easily recleanable. Going with your figures and some others it would appear that felt is the best choice. Since my shop is a combination wood and metal I would be very interested in metal central collection of the swarf and if it is possible or practicable.
Great points Douglas. I since posting this I upgraded to a 42 inch 1 micron felt filter. Was $40 from Rockler. Has great air flow and great filtration and was many times less expensive than a canister.
Great follow-up video. I have done similar tests in my own shop before. Sometimes outdoors is significantly less than my shop and sometimes the opposite. Outdoor particulate levels vary a lot depending on weather, local pollution levels, landscapers running leafblowers, neighbor's diesel pickup, etc., etc. IF you live in a city with high pollution then I would expect outdoor particulate levels to be worse than your shop, but that isn't really a good argument for why you don't need a HEPA cartridge filter on your DC in your shop IMHO. Bottomline is that around 0.3um particulate levels are just hard to filter due to Brownian Motion causing degraded filter efficiency in this range. A bag filter is just much less efficient at capturing particles around 0.3um than a HEPA cartridge is, but whether or not you want to pay for a better filter is totally subjective. I just wouldn't use outdoor air particulate levels as my baseline...I strive to have my shop, and house, be much, much cleaner than outdoors because this is where I spend most of my time so it has the most affect on my health. With proper filtration, IAQ should be far cleaner than outdoor air in most locales.
RF Guy - Thanks for the comments. I'm curious if outdoor air is not a good baseline, then what is a good baseline? Also, what are your particle counts running your cyclone/HEPA canister system?
BTW -
www.airnow.gov/ - On the day of the test, my area (and most of the country) was at PM2.5 70 Moderate. Today it is PM2.5 28 Good for my area and most of the country.
EPA has long recommend ventilating outside air as a major strategy for improving indoor air quality. www.epa.gov/indoor-air-quality-iaq/improving-indoor-air-quality
@@woodshopnerdery For a baseline, you could target the green range in the AQI recommendations from the EPA, but I don't even think the EPA specifies or measures particle counts below PM2.5 unfortunately. My approach is as follows: I run my air cleaner in my shop when it is not in use, so when I enter my shop to work, I use this level as my "baseline". I mainly focus on the 0.5μm range on my Dylos which is typically around 200 or less. Then as I am working, I just keep an eye on the Dylos. Usually it stays under 400 for most operations, but for certain sanding operations it can climb above this. Whenever the counts get above 1000 (like some sanding operations), I take a break from my shop and come back a short while later to resume work. I am not saying everyone should do this, but this is just my method. This works for me with the Dylos because each reading is averaged over 10 samples. It is much harder to implement this method with meters that are instantaneous reading only because it fluctuates so much reading-to-reading. Bottomline is I try to keep my shop close to the particle count levels that I maintain inside my home. I also run air filters in my house so my IAQ is better than the average home. The EPA ventilate to outside rule only really works when the outside air is cleaner than inside right, but what if you live in a big city? Ventilating to the outside means also pulling in outside air to replace it to maintain pressure inside the house. IF you live in a very polluted area it may be inadvisable to ventilate outside because you'll pull in much more polluted air from outside to replace it...
Great method. And a good set of goals. I think I have been doing something analogous, but maybe not as rigorous and with somewhat more relaxed goals.
I look mostly at the AQI screen because I can see it across the garage, it shows a single value in large font. It normally stays in the "Good" range but during some operations spikes into the "Moderate" range but is within minutes cleaned back up to "Good". And boy if I forget to turn on that dust collector, then numbers go way up, and yes I do turn on both my systems and come back in 10-20 minutes.
I know the AQI is not a perfect measurement. I like your 0.5 micron approach. But like you said, on my unit the detail screen shows instantaneous measures, so it can be quite "peaky". That is why I showed the min and max values in my video. But on my unit I believe the AQI "estimate" is calculated over several sample reading across all practical sizes. Not the 24 hour period spec'ed out by the AQI standard by it is a "rolling average" of some sort. So I try to keep it in the "green" and also look at the trend up or down and try to make sure it trends downward between operations.
If money were no object I would go with the Oneida Mini-Gorilla. It seems like it would meet my needs while still fitting in my limited space. I think that sort of upgrade is what it would take to get an appreciable change over what I have now. I think if I simply swapped my felt for pleats it would not be a game changer.
@@woodshopnerdery Yeah, I think you are on the right track with all of this. I am not saying my method is the only way to do it. I mainly just wanted to highlight that outdoor air quality can be crap in some areas so I wouldn't use that as a baseline. I am also a strong advocate for HEPA cartridge filters, but I know they come at a cost and may not be suitable for everyone. I really wouldn't recommend anyone switch to HEPA cartridge filters unless they can afford the airflow drop with putting a cyclone in front of the DC first. Otherwise as soon as the cartridge filter clogs up, their airflow will drop precipitously which will compromise dust capture at the tool resulting in even more dust particulate entering the shop atmosphere. For me, I try to keep my shop as clean as possible...hopefully close to my indoor AQI levels. My shop is in an attached garage so entering/exiting the shop allows some of that air to interchange and I really don't want any of that dust getting into my living space. As a result, I may be more rigorous with my approach to all of this, but for good reason. With regard to instantaneous readings on particle counters, I have been meaning to try to hookup one of those PlanTower sensors to a laptop so that I could do my own averaging and data display. It would definitely be more useful with a running average and histogram display to see how different shop operations affect shop air quality.
Another suggestion is to measure with and without bag on your dust collector. And compare the numbers with and without the reducer. I would also suggest that you use a y fitting to split the 4 inch and use one on the dust port and another as an auxiliary port near to not big down your dust collector.
Aravindah, thanks for the suggestions. I totally agree with you. I did do what Oneida Air calls, "Free Fan" testing with an Anemometer in my first video on my dust collector. I found that the coupler/reducer is by far the biggest bottleneck in the system and concluded that getting a canister filter is not guaranteed to improve the air flow.
Here is the video if you are interested - ua-cam.com/video/IeXHpUmrNVM/v-deo.html
Also, great call on the splitter. To avoid buying a second machine to collect dust from my orbital palm sander, I use this same dust collector. But, I add a 4 inch to 2.5 inch Y adapter to allow "make-up air" to flow into the 2nd port since the sander is very restrictive on air flow. The purpose, as you say, is to avoid bogging down and stressing the motor. But it has to be in balance, I find that I must block about 60% of the open Y port to maintain sufficient air flow through the sander.
Tend to think that the kind of material you typically work with (species of wood in this case) and your reaction to that wood and its dust is the bigger issue. Most wood dust is very irritating to lungs but for some extremely more so. In those situations a "better" or finer filter is pretty much a given if you plan to continue in the hobby. Obviously other factors like exposure time, duration, and machinery used are all pieces of information for the health puzzle. Clearly a hand plane has less of an impact to dust creation that a 3-HP router. Or compare impact of working Cocobolo or Rosewood to Alder or Birch. Hardwoods versus man-made composites like MDF. Base line is if you aren't cleaning your nose regularly or often then you mIght be OK but be cautious as your activity ramps up.
Thanks Don. I totally agree that wood dust and especially fine wood dust is a serious hazard. I did purchase a 42 Inch 1 micron bag from Rockler for $40 since making that video and it's working well.
Very interesting results, Thomas. You are living up to your channel name! Have you installed a Thien baffle in your dust collector? Scott
Thanks, I really enjoy this kind of inquiry in addition to making projects. I'm trying to keep a balance of both types of videos.
Yes, I have looked into the Thein baffle, bucket separators, and cyclones. Although the mechanisms are different they all employ gravity to separate heavier materials from lighter BEFORE the fan. They also lower the CFM quite a bit initially but help maintain CFM by preventing the filter from clogging. This is good for shop vacs because once the filter is clogged the CFM goes to almost zero anyway and the filter is a total pain to clean.
To start I had a tool box style Rigid vacuum, then I added a Dust Deputy, which kept the filter clean and the vacuum running at peak (~80 CFM maybe?). But it was irritating to move around and always fell over. I looked into building a cart but realized that if I was going to dedicate floor space to a cart I might as well invest in a proper dust collector. So I purchased the unit I have now, it was an amazing difference in air quality, cleanliness and generally enjoying my time in the shop more.
In my opinion I would not benefit from a pre-fan chip separator like a Thein baffle; 1. I have a metal fan so no need to protect it from chips, 2. it's a small system so I don't have extra CFM to spare, 3. my felt bag can be cleaned with a few taps to restore optimal CFM so no need to protect the filter from clogging. 4. true bag-bottom, filter top dust collectors like mine already separate materials using gravity.
The one exception is on some rare occasions when I use the planer and jointer I do get a clog at the inlet of the dust collector motor housing. In this case I could benefit from a pre-separator. But, to clear it out takes 1 minute and I don't want to store a separator when I only need it 1% of the time. Hmm... now I'm thinking...
When I got my dust collector I gave my Dust Deputy to a co-worker for his garage shop. They work wonders for shop vacs, but for my system it would eat away my CFM because they do that and because it would require I use a 2.5 inch hose instead of a 4 inch hose which also is a CFM killer.
There you go some bedtime reading😴😴😴😴😴😴😴
@@woodshopnerdery The original Thein baffle wasn’t pre-fan and was actually designed to be installed inside a dust collector like yours. I agree with your assessment or the pre-fan separators.
I had not heard of an internal Thein baffle. But I looked it up and learned we are spelling it WRONG, should be Thien. Anyway, no I don't have one. Is the purpose to prevent the inlet air from stirring up old dust in the lower bag? Have you added one to your dust collector? Is it having an impact?
@@woodshopnerdery Ok, so it looks like you've learned the first lesson, and that's you should never look to me for proper spelling! I used to say that I spell atrociously, but then my bride pointed out that no, I can't! Anyway, no, the point is to get the dust to drop out of the air before it hits the filter. It's not unlike the cyclone that is already designed into your separator but even more effective. I have a SS DC3300, so I can't install one, but I may buy another, larger DC and if I do I'll install one in it. Scott
@@MyGrowthRings I'll have to put some thought into it. I guess it's suppose to give the dust a longer arc of travel in a slower air stream so it can drop out? Interesting.
I purchased the SSmith upgrade DC motor. The amount of air moved by the new motor is significant. I removed the 3 way intake on the DC 3300 and in its place installed a 4” connector. As well I ordered and am using a 4” hose from the DC to the Smith. I purchased a 4” to 2-1/4 reducer, clamped about 12” of 2-1/4” length of hose enough to move the table or headstock without interference. The lack of sawdust, bandsaw dust, improvement of conical disk dust is - well I’m glad I purchased the new motor, connectors and hose.
Ok - but!! It’s foolish to argue against data I know but - are you sure you didn’t confuse the two data sets?
That outside air has more particulate matter than inside air? There’s (me thinks) an error- - - -?
Hi John, thanks for questions.
I don't read too much into the data. Its just engineering field measurements and NOT a lab setting scientific study. I think of it as akin to reading my own body temp as a diagnosis for an illness. I was simply "taking the temperature" of my dust collector to see if I could find any common "illnesses." I don't see any right now.
I think you have a great setup with the DC6000. And running the 4 inch hose as long as possible before reducing to 2.5 inch removes A LOT of friction from the system which avoids major drops in CFM.
I don't think I confused the data sets because I watched the video several times while editing and you can see right within the footage some of the numbers at each location. All the outside measurements prove to me is that my device is capable of reading higher values.
@@woodshopnerdery
I too watched and confirmed exactly what the data shows. However - that said…. you are in a confined space. Dust is being generated. The dust can go into the collector and some of it won’t. The hood too is “open” enough that ….
I don’t get it - I’ll be …….!👍👍
And I’ll say again the audio and video quality is most excellent. Nicely done.👍👍
Thanks for the compliments. I've been trying to get the best audio and video I can with the equipment I have, iPhone, cheapo camcorder, computer mic. I wish it were better, but this is just a hobby for me so... I used Shotcut to put it together which is a very basic free application.
Don't get me wrong, I am concerned about the dust. I know very well that broadly speaking 50% of the dust is not collected immediately. This is why I have the ambient filter. But, there is only so much a dust collector can do. I have adequate CFM and my filter is capturing particles of all sizes. So it is helping. Could I invest $1500 and do better, of course I could. But when is good enough, good enough? I'm still trying to discover these answers.
I think that there is a popular misconception with filters that it either gets 95% of 0.3um particle or it gets NOTHING and lets EVERYTHING through. That is not true as far as I can tell. My filter is still getting the particles, but instead of 95% efficiency perhaps as a best guestimate maybe only captures 80% of 0.3um. So if I cycle the air twice through my system does the filter get 96% (80% + (20% x 80%))? I think my test showed some indication of that, the longer it ran the more the particle counts dropped.
PS I used to use Shopsmith 3300 and this is a lot better. Sure the upgraded SS is good but expensive.
I would have bought a Shopsmith DC but at the time the DC-330L was out. That looked to me like a Rikon 60-100 with Shopsmith labels on it. So that is why I looked off brand. Glad I did. This Shop Fox is a great value. I may upgrade to something else one day, but its working great for now.
BTW - Thanks for watching and commenting. I really appreciate it!
Really like the data! Thanks. Do you have a link to the particle counter in this video? It seems like everyone who is doing a video with CFM measurement should always do one reference point at the entrance to the dust collector. Variations after that are infinite.
The particle meter is a cheapie from eBay. I can’t give a link because the listing changes every few weeks. That one has since stopped working and I purchased a Dylos brand unit.
I did use a anemometer in the first video to measure the intake. The method I used in this video is inspired by Oneida’s real world testing methods, which involves a pitiful tube at the end of a 10 foot hose. That would be the minimum resistance any system would have but still is plausibly usable.
So this is what it would have been like if Mr. Wizard would of had a woodshop... Just joking Thomas, great video.
Thanks Chad! Well, I tried to warn people by putting "nerdery" in the title.😁
another awesome video! agree the canister setup may not really provide much more protection But here is the thing, don't put all your donuts in the air filtration alone USE a good quality N95 or similar face mask when cutting, sanding, grinding, spraying in an enclosed space with poor outside air circulation! Oh and another thing, Great Scott! if DOC Brown had you as an assistant who knows perhaps the "BTTF" Time Machine could've been a Ford Mustang instead of a DeLorean! Wait a minute, you didn't use this whole nerdery experiment to build your own time machine so that you could back into the future and kiss an 18 year old version of your mother? {okay probably not very appropriate comment but it did happen in the movie, so just saying!}. all seriousness, this one video probably solidifies your spot in the Nerdery video Hall of Fame, truthfully it is that good. thanks for sharing.
Thanks for the compliments! And thanks for the nudge on the dusk mask. I worked myself into a really good habit of wearing either an N95 or a Respirator. But got out of that habit in 2020 when I could not buy replacements. But the N95s are on the shelves again and I NEED to get back into that routine.
Very helpful - thanks. I have the same dust collector ( bought only craiglist brand new before seeing this video ) and also 2 1/2 inch at tools (shopsmith) . I tried your set up and I am now experimenting with a y at dust collector 4 inch to pair 2 1/2 outlets and using 2 1/2 hose to one tool and other outlet open or 2 hoses to 2 machines. It seems to work better than 4 in hose with reducer - I have tapered reducer similar to yours. I can not do any measurements though. What do you think ? I also have cloth filter and had canister envy but no more - thanks - money for some other toy.
John, I did do some testing for the first dust collector video on my 2.5 inch hose. I did not include it in the video because honestly I did not consider it a viable option. I put the reducer directly on the DC and then ran a 10 foot 2.5 inch hose. Note my 4 inch hose is also 10 foot. At the end of the 2.5 inch hose I measured 87 less CFM than I measured at the end of my 4 inch hose with the 4 to 2.5 reducer. The measurement I got for the 2.5 inch hose was 110 CFM, which is about the same as Shop Vac.
Friction between the air and the side wall is the enemy. Larger diameter hoses have a greater cross section area per linear unit of circumference than the smaller diameter hoses. In other words, larger hoses have less friction per volume. The conventional suggestion, which I see all over the place, is to run the largest diameter hose or pipe possible until the last possible place, then reduce to smaller.
Keep in mind that with a DC you want high air volume movement. The air may have a higher linear foot per minute rate at the end of a 2.5 inch hose, so to the eye and hand it looks and feels like better performance because the air is moving faster. But the goal is to get better air volume movement, while still maintaining a minimum of about 4000 feet per minute flow rate. Common wisdom is that air moving at 4000 fpm keeps the particles suspended in air so they can be collected.
Doesn't really ADDRESS the question posed in the title of the video.
You're just making an assumption based on data collected ONLY from a bag filter. You really need to buy a HEPA or 1micron canister filter & compare the numbers to the bag filter results in order to address the question.... Canister filters DO improve airflow, which even with 2.5" reducers should show a measurable difference.
The real question is how much improvement is there in changing from a bag filter to a canister filter.
No it did address the question. There would be little to no improvement on my machine. Look at the "free fan" measurements without any filter vs the "clean bag" measurements. There is only a 5 cfm difference. So assuming these expensive canisters have 0 air flow resistance (with is impossible) I would only get 5 addition cfm out of it. And as the difficult to clean pleated filter became impacted with dust the cfm would drop significantly well below the bag filter.
Canisters manufactures should list the cfm per square foot of material and the total square footage.
BTW after this video I bought a 42 inch 1 micron bag filter from Rockler rated at 50 cfm per square foot. It was only $40 and supports more than enough total air flow for the capabilities of my machine.
that AirNow ppm meter detector is the weak point in your analysis. It is an inaccurate and unreliable device to base your assumptions and conclusions on.