Discover and read the best of Twitter Threads about #BoxFanFilter

Most recents (8)

I promised I would provide a way to calculate room air exchange, using a simple MERV-13 filter & a box fan. The sweet spot seems to be 6 exchanges per hour. This means all the air in the room is moved through the filter 6 times in 1 hour. 1/6 #ProtectHCWs #ProtectKids #Covid #BA2
First we need to get the volume of a room. It doesn’t need to be perfect! But note units are important. We are using feet/inches here. Use this calculator & input the measurements, A, B, & C as shown in the graphic below. Order is NOT important 2/6 #Filter…
I found a company that did calculations using a box fan on high speed & MERV-13 filters of different depths. The thicker the filter the BETTER the air flow! Strange but true. Note I added the Air Volume based on a 20” square box fan. 3/6 #N95 #BoxFanFilter…
Read 6 tweets
"6 Questions To Ask Your Colorado School About COVID And The Air In Your Child’s Classroom"

Great, well-researched & hyperlinked article in @CPRNews by @CPRBrundin

These are not rhetorical questions -- pls contact your #school district!
🧵 below (1/x)…
2/ Also don't miss the link to answers from 25 #Colorado school district on their COVID response. Brilliant & critical public health info!

Using this info you can follow-up based on the questions @CPRBrundin provides!……
3/ #AskYourDistrict:
1. How is the air in your child’s classroom being filtered and ventilated?

- Improve to MERV 13 filters, minimum of 5 ACH air exchange, and open outdoor air dampers
- Don't forget the long-term benefits
- Way to go @ESDk12 for using federal $ on air upgrades
Read 11 tweets
Tweets featuring mass production of do-it-yourself box fan air filters. Photos by @astrochilanga @native4data @ROCPassiveHouse. Tag @DavidElfstrom to add more!…
Jim @JimRosenthal4 if you happen to come across mass production of box fan filter/cubes let me know and I'll update the twitter Moment above
Read 4 tweets
#boxfanfilter optimizing:
Fan shroud sizing for Lasko 20" Comfort Fan /1
Drove a screw into the middle /2
Made concentric circles with dry-erase marker /3
Read 15 tweets
A 🧵 to counter some confusing messages about masks & wildfire smoke (1/x)

1. High-quality masks (i.e. #N95) best for both viral aerosol + #wildfire smoke
2. N95s readily available & should be used for both
3. But other masks can provide non-zero benefit…
2/ The #CDC and #EPA both strongly recommend upgraded masks (respirators) like #N95 or #KN95 to protect against wildfire smoke. I totally agree (unless using something even better like N99 or elastomeric), b/c these filter the smallest particles very well.…
3/ But the #CDC also says not to use N95s, b/c they "should be reserved for health care workers." I totally disagree, as do countless others, b/c supply chain problems in 2020 have recovered in the US.

Follow @projectn95 & see resources to easily buy.
Read 15 tweets
Frequently questions about type of room air filtration & if #ionization is a useful upgrade.

Nearly always, simple filtration is sufficient for most people. Study here shows a bipolar ionizer also *not* useful at reducing PM2.5. Thx @JimRosenthal4. (1/x)…
2/ "[experiments] ... suggest that operation of the ionizer unit led to a small increase in loss rates for ultrafine particles (<0.15 μm) and a small decrease in loss rates for larger particles (>0.3 μm), but with negligible net changes in estimated PM2.5 loss rates."
3/ In contrast to relative ineffectiveness of ionization technology to reduce concentration of suspended particles in a room, simple #HEPA filtration does an *excellent* job. See e.g. examples in this 🧵 showing filtration in a school classroom.
Read 7 tweets
1/ Interesting paper showing high efficacy of portable HEPA #filtration to reduce aerosol concentration in a high school classroom during use.

By very experienced German aerosol group Curtius et al.; via @ASTJournal.

With short🧵on room air filtration.…
2/ "In times when classes were conducted with windows and door closed, the aerosol concentration was reduced by more than 90% within less than 30 min. when running the purifiers (air exchange rate 5.5 ACH). The reduction was homogeneous throughout the room ..."
[note log y-scale]
3/ Figure 3: Highly reproducible reduction in aerosol particle concentration [uCPC] in a closed classroom without air purifiers (blue line) and with 3 or 4 air purifiers operating at speed 3 or 4 (max).
Read 15 tweets
1/ During July 2020 many worked quickly to scramble #COVID19 prep before the Fall classes. I helped model estimated COVID #aerosol risk as @UofDenver made plans. Not allowed then, but shared now in case it can prompt discussion for Winter prep.

Doc + 🧵:
2/ A key concern at the time (& still) was #music ensemble classroom activities, b/c it was obvious early on that #COVIDisAirborne and that #choir & wind instruments were likely to present high COVID #aerosol risk.…
3/ Using my version of an aerosol #boxmodel, I calculated probability that #SARSCoV2 could infect after breathed out by someone in specific classrooms. With this I could easily investigate best prevention bang for buck. I.e. Rehearsal duration? Wait time b/n classes? Etc.
Read 20 tweets

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