Thread by @CorsIAQ

1/ One of my slides. Cost of good portable HEPA filter system in a 600 to 800 square ft classroom with 25 students (equivalent ACH increase of 2.7 to 3.5/h). Cost is broken down by classroom and student.

2/ Cost = year 1 capital cost + annual recurring costs for filters + electricity at $0.11 per kW-hr.

Total 3-year cost per classroom < $790 (< $11/student for 75 students over 3 years).

3/ If school has 50 classrooms (larger than my K-8 school) the total cost over 3 years < $40K for entire school. Less for less classrooms.

If noise is an issue can go with 2 HEPA air filters per classroom at lower setting for around $20/student.

How much do books cost?

4/ Maintenance time. I timed myself switching out three HEPA filters in a single portable HEPA filter system last Friday for the units I purchased in my building @Portland_State. It took slightly less than 4 mins.

5/ This will likely have to be done twice/yr in each classroom w/ some caution (careful, wear mask, filter into plastic bag, sealed, wash hands). Turn system off on Friday afternoon and replace filters on a Monday morning.

6/ This is a proven technology, folks. The cost per student is small and the overall cost to the US is very small compared to what schools will be receiving, the overall inhalation dose (and risk) reduction, and benefit toward re-opening schools. Just Do It!

6/ Note - This is only for classrooms and does not include other spaces in schools, some of which are too large for reasonable consideration of $250 HEPA filters (e.g., gymnasiums). But the classroom environment is critical. So let's get that done right.

7/ Along with masks and distancing and increased ventilation where possible, etc., portable HEPA filtration systems SHOULD be considered to reduce inhalation dose and risk. Just Do It!

To be absolutely clear, I do not endorse any of the products that are being added as replies to this tweet thread.