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Apr 14 • 3 tweets • 3 min read
As box fans return to store shelves in advance of cooling season, will @Lasko_Products bring an optimized and safety-approved #corsirosenthalbox fan and filter frame kit to market? Even Lasko's AirFlex model could be greatly improved.
@Lasko_Products @Lasko_Products note the large purchases of your box fans to make air filter products suitable for the large volume of classrooms. Many jurisdictions refuse #corsirosenthalbox due to lack of safety certification despite EPA & UL blessing. You can help! twitter.com/i/events/14277…
@Lasko_Products @Lasko_Products, team up with @3M and work together! 3M has already tested their filters with your fan in lab tests of #corsirosenthalbox.

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More from @DavidElfstrom

David Elfstrom Profile picture
Apr 10
Thread on why a typical building may be safer in spring and fall than any other time of the year:
Mild temperatures during the shoulder seasons result in the highest outdoor air change rates compared to winter and summer: /1 Scatter plot showing at low and high outdoor temperatures th
This is because of the economizer function on HVAC equipment. Due to solar gains and heat from people and equipment, it's warmer inside than outside. If the outdoor air is cooler than inside, use it instead of running mechanical cooling (air conditioning). /2 Outdoor air fraction for an idealized economizer cycle showi
We get the most outdoor air when an outdoor air damper is fully open, typically at the switchover point between heating and cooling (~15°C / 69°F). /3 Scatter plot showing at low and high outdoor temperatures th
Read 6 tweets
David Elfstrom Profile picture
Apr 4
The next time someone denies the use of a portable air cleaner in a classroom on a (false) basis that it might spread infection by moving air, or interfere with the HVAC system, show them this paper. @amandalhu @sameo416 (HT @Poppendieck).
onlinelibrary.wiley.com/doi/epdf/10.11… /1
When determining the amount of outdoor air provided to a space, ASHRAE Standard 62.1's Zone Air Distribution Effectiveness factors to account for the inefficiency of air delivery and mixing to provide outdoor air to the breathing zone. /2
For example, in heating mode, with a ceiling level supply and return, the effectiveness is only 0.8. So we need to provide 25% more outdoor air. (image: User's manual for 62.1-2010) /3
Read 18 tweets
David Elfstrom Profile picture
Apr 3
Insufficient ventilation at arena causes fog in the stagnant air over the ice between the plexiglass. CO₂ rose constantly without end until intermission, when we left, at 2000 ppm.
Great show! We wore our respirators, few others did. Some coughing behind and beside us.
Dew point was approximately 4.5°C
CO₂ in arena changeroom with a dozen skaters: First spike when changing, slow decay while vacant, then rises when changing again, slow decay while vacant, final spike when come back.
Only mask was on my daughter, a CA-N95 taped at the top to ensure fit.
Read 8 tweets
David Elfstrom Profile picture
Mar 21
The power was out this weekend so I decided to reclad the ELFSTRÖM in final permanent form: /1 Box fan with outlet shroud and box mounted on the inlet side
I used vinyl adhesive shelf liner to wrap the box. Still using painter's tape to mount the filter - makes it easy to change the filter and won't ruin the vinyl adhesive pattern. The filter gets sucked on when running anyway. /2
The box is mounted to the fan on the inside, making the outside connection tapeless. /3
Read 4 tweets
David Elfstrom Profile picture
Feb 2
Highly recommended! Detailed summary of the main engineering controls for airborne infection control to reduce transmission indoors:
#Ventilation #Filtration #UVGI
👇
#DoAllTheThings! Implement multiple engineering controls to reduce airborne infection and improve indoor air quality
#Ventilation
#Filtration
#UVGI Image
If you want a partial data dump of my brain, the Time Magazine article is a great summary. time.com/6143799/covid-…
Read 4 tweets
David Elfstrom Profile picture
Jan 20
Having a CO₂ meter with visible display can enable an educator to be a manual version of a demand-controlled ventilation system, with control over the indoor environment using windows (Source: Di Gilio et al 2021, pubmed.ncbi.nlm.nih.gov/34224708/) #COVIDCO2
HT @Billius27 "Fig. 5 are shown the ...
@Billius27 If a CO₂ display was in my daughter's mechanically ventilated classroom, her teacher might have opened the windows, or moved to another room after seeing rising levels. Principal: waiting for parts to repair the HVAC system. Daughter developed common cold symptoms 48h later. Image
@Billius27 Here is one of many reasons WHY we want to monitor and take action on CO₂ concentrations:
Read 4 tweets

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