<aside> ❓
Resources and guidance related to testing filter performance outside professional labs.
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Discussed in a Facebook group post here.
Goal: Establish a simple way for the community to collect approximately "apples-to-apples" data at a reasonable price so we can improve the Clean Air Stars dataset (or build our own).
Manufacturers tend to publish only "sleep mode" noise levels and "snowblower mode" CADR. This isn't helpful when what we need is the CADR/noise combination that maximizes efficacy at a tolerable noise level for a classroom. So let's identify a relatively affordable sound meter and anemometer as the recommended ~$50 "kit" for community members with the means and the inclination to help.
Sound meter: Perhaps **https://a.co/d/ht2rCZ6** (TopTes TS-501A) for ~$25, which is factory-calibrated and includes the ability to do A-weighting. (Are there other important features to look for at a low price point?) Then we standardize on a community testing protocol: something like "3ft up, 3ft away, room bigger than xx sqft, no carpeting, confirm background noise, etc." This will help with a rough sense of how filter noise compares, since manufacturer data is almost never standardized (like AHAM AC-2) or reliable.
Anemometer: Perhaps **https://a.co/d/1mql6kR** (HoldPeak 866B) for $30, which has a larger diameter than some and a tripod mount hole if needed. [Tony](https://www.facebook.com/groups/742150840145010/user/515188243/?__cft__[0]=AZVQJ3Hx5VDMSCcxCZCehCGtaSeLu6uazH7FtJkp90ZzUH7Hw7dgJ_0jEjx38GXu2HuU5NIyisUFMUEYg1vIbRh0XH0HhHJQUGqrko8rpQyRWtScehYv2aH8oLkjb8YNWMLO2aUXC9BTnNYInIkgC5UfAjtfGkPb-vPoCu2E1r5CFHNTaDfwAsc_6RpzHXueQek&__tn__=-]K-R) has been educating me on how challenging it can be to get consistent data, since the placement of the anemometer next to the discharge matters a lot. Those numbers won't be comparable across setups, or even across filters in the same setup. But: say a manufacturer publishes a trusted (AHAM AC-1, etc.) value for its top speed, like 300 CFM. If you take an anemometer, put it on the discharge vent and measure the velocity at that top speed, then (without moving it!) the velocity at a tolerable noise level ("Speed 2," let's say), you could calculate a percentage (e.g., tolerable speed is 60% of top speed). Is it fair to say as an approximation that the CFM at "Speed 2" is roughly 60% of the 300 CFM published as top speed CADR?
I realize that math is far from bulletproof, but if it's plausible as an estimate, it would help enormously, given the data for intermediate speeds is rarely published (by anyone except Medify). Thoughts, group experts ([Bill](https://www.facebook.com/groups/742150840145010/user/1128366150/?__cft__[0]=AZVQJ3Hx5VDMSCcxCZCehCGtaSeLu6uazH7FtJkp90ZzUH7Hw7dgJ_0jEjx38GXu2HuU5NIyisUFMUEYg1vIbRh0XH0HhHJQUGqrko8rpQyRWtScehYv2aH8oLkjb8YNWMLO2aUXC9BTnNYInIkgC5UfAjtfGkPb-vPoCu2E1r5CFHNTaDfwAsc_6RpzHXueQek&__tn__=-]K-R), [David](https://www.facebook.com/groups/742150840145010/user/760305079/?__cft__[0]=AZVQJ3Hx5VDMSCcxCZCehCGtaSeLu6uazH7FtJkp90ZzUH7Hw7dgJ_0jEjx38GXu2HuU5NIyisUFMUEYg1vIbRh0XH0HhHJQUGqrko8rpQyRWtScehYv2aH8oLkjb8YNWMLO2aUXC9BTnNYInIkgC5UfAjtfGkPb-vPoCu2E1r5CFHNTaDfwAsc_6RpzHXueQek&__tn__=-]K-R), [Jim](https://www.facebook.com/groups/742150840145010/user/1708719247/?__cft__[0]=AZVQJ3Hx5VDMSCcxCZCehCGtaSeLu6uazH7FtJkp90ZzUH7Hw7dgJ_0jEjx38GXu2HuU5NIyisUFMUEYg1vIbRh0XH0HhHJQUGqrko8rpQyRWtScehYv2aH8oLkjb8YNWMLO2aUXC9BTnNYInIkgC5UfAjtfGkPb-vPoCu2E1r5CFHNTaDfwAsc_6RpzHXueQek&__tn__=-]K-R), [Michael](https://www.facebook.com/groups/742150840145010/user/641236214/?__cft__[0]=AZVQJ3Hx5VDMSCcxCZCehCGtaSeLu6uazH7FtJkp90ZzUH7Hw7dgJ_0jEjx38GXu2HuU5NIyisUFMUEYg1vIbRh0XH0HhHJQUGqrko8rpQyRWtScehYv2aH8oLkjb8YNWMLO2aUXC9BTnNYInIkgC5UfAjtfGkPb-vPoCu2E1r5CFHNTaDfwAsc_6RpzHXueQek&__tn__=-]K-R), etc.)?
Even if it falls well short of the confidence AC-1 and AC-2 give us ("the perfect is the enemy of the good" and all that), I'm not succeeding in getting mainstream manufacturers to share that. We want to put them on a level playing field with the data folks like [Clean Air Kits](https://www.facebook.com/groups/742150840145010/user/100084111080684/?__cft__[0]=AZVQJ3Hx5VDMSCcxCZCehCGtaSeLu6uazH7FtJkp90ZzUH7Hw7dgJ_0jEjx38GXu2HuU5NIyisUFMUEYg1vIbRh0XH0HhHJQUGqrko8rpQyRWtScehYv2aH8oLkjb8YNWMLO2aUXC9BTnNYInIkgC5UfAjtfGkPb-vPoCu2E1r5CFHNTaDfwAsc_6RpzHXueQek&__tn__=-]K-R) and [Adam Xie](https://www.facebook.com/groups/742150840145010/user/100001790812620/?__cft__[0]=AZVQJ3Hx5VDMSCcxCZCehCGtaSeLu6uazH7FtJkp90ZzUH7Hw7dgJ_0jEjx38GXu2HuU5NIyisUFMUEYg1vIbRh0XH0HhHJQUGqrko8rpQyRWtScehYv2aH8oLkjb8YNWMLO2aUXC9BTnNYInIkgC5UfAjtfGkPb-vPoCu2E1r5CFHNTaDfwAsc_6RpzHXueQek&__tn__=-]K-R) are giving us. Comparing to the max-CADR and min-noise values published by the likes of Levoit and Coway isn't helpful or fair, to say nothing of the even less trustworthy manufacturers.
Naturally, if these aren't the right units to recommend, suggest different ones, please.
<aside> ↩️
Back to the Safe Indoor Air Resources homepage at safeindoorair.org.
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