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Richard Corsi, PhD, PE (Texas) Profile picture
@CorsIAQ
Nov 16 • 10 tweets • 2 min read Twitter logo Read on Twitter
1/ Canadian's beware. An article in Canada's National Post yesterday contains misleading information RE promotion of round-the-clock hydroxyl radical (OH) generation in homes. I have purposely not included a link here.
2/ OH radicals do not "neutralize" indoor air and should not be seen as "keeping your indoor air clean" or to "improve the air you’re breathing." OH radicals are HIGHLY reactive and lead to a wide range of chemical reaction products (by-products) in indoor air.
3/ Some of these by-products are known to be harmful. Some are suspected to be harmful based on their chemical structure and similarities to chemicals we know can be harmful, and we do not have good tox data for the majority (those may or may not be particularly harmful).
4/ OH reactions also lead to the rapid formation of ultrafine secondary organic aerosols (SOA), and emerging research suggests growing concerns regarding inhalation of ultrafine particles, their transport and deposition in the brain, and more.
5/ So, I think it is misleading to state that these systems improve the air we are breathing or neutralize indoor air, or keep indoor air clean.
6/ Adding chemicals to indoor air to clean it is not the answer to healthier indoor air. The answer goes back to the 3Rs of healthy indoor air: Remove the source. Reduce the source. Remediate the air. The latter should occur if the first 2 Rs are impossible or met with failure.
7/ When we remediate indoor air we should directly remove (subtract directly) the pollutant by ventilation (of pollutants emitted by indoor sources), media filtration (for particles) ....
8/ activated carbon for VOCs, gas-phase SVOCs, and ozone, zeolites for selective VOCs, or effective passive removal materials such as clay-based wall coverings for ozone and organic acids.
9/ Improve indoor air by removing pollutants from the air directly. Remove the source. Reduce the source. Remediate the air by removing pollutants directly and NOT adding chemicals to air to try to remove some pollutants while creating others.
10/ It's not rocket science, folks.

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More from @CorsIAQ

Richard Corsi, PhD, PE (Texas) Profile picture
Oct 30
1/ So appreciate @DrLaPook's continued focus on the importance of indoor air quality & @60Minutes for having @linseymarr & @j_g_allen on the show to discuss the fact that COVID-19 is an airborne infectious disease & has always been despite claims of many "authorities." GR8 job!
2/ Been working on IAQ for decades, doing research & teaching many undergrad & grad engineering classes on it. But few universities even offer 1 course on indoor air quality. As @j_g_allen stated, it's largely been missing from discussions of public health. Univ's included.
3/ This has been to the disappointment & frustration of many who have toiled in the field for decades & stayed committed to the cause, but who have failed in having the outcomes of our research or our voices lead to a level of societal acknowledgement of the importance of IAQ.
Read 7 tweets
Richard Corsi, PhD, PE (Texas) Profile picture
Oct 14
1/ Just saw that a company w/ a relatively expensive air cleaner is criticizing #CorsiRosenthalBox es. I wonder why? There are more peer-reviewed journal articles on the CR-Box than their product.
2/ Critical or our @ucdavis study that showed CADR that BLOW other systems away, implying the results seem too good and need to be replicated. Would love to see their data, replicated and in a peer-reviewed journal.
3/ We used the same experimental process to test our CR Boxes in replicate as we did for commercial HEPA air cleaners and arrived at the same CADR listed by manufacturers for two commercial HEPA air cleaners (protocol worked!). Were those companies lying about their CADR?
Read 6 tweets
Richard Corsi, PhD, PE (Texas) Profile picture
Oct 11
A bit of preliminary data on the CR Box in the @UCDavisCOE dean's office suite - one of several in our on-campus field study. CADR & effectiveness. 1/ Image
Effectiveness (e) is defined as 1 - Cw/Cwo, where Cw = PM2.5 concentration with the air cleaner in place and Cwo is the PM2.5 concentration without the air cleaner in place. 2/
For a nearly 400 ft^2 shared space in our office suite the effectiveness remains at between 0.93 and (indiscernible from) 1.0. In other words, our CR Box is reducing the amount of PM2.5 we breathe in by 93% to nearly 100% relative to w/o the CR-Box in operation. 3/
Read 11 tweets
Richard Corsi, PhD, PE (Texas) Profile picture
Sep 21
1/ After more than 15 mos & 3,300 hours of operation this CR-Box was tested & sent to CR-Box pasture about 2 mos ago. It was just recalled (with no hesitation) for service while its replacement is going through a suite of 2-month lab testing as part of our field study. Image
2/ Importantly, even after 15 mos and more than 3,300 hours of actual operation this CR-Box maintains an average CADR (high flow) of about 400 cfm (for particles between 0.35 and 3 microns) w/ over 500 cfm for particles greater than 2.3 microns.
3/ The PM2.5 concentrations outdoors and indoors have been relatively high the past couple of days and this extensively used CR Box with soiled filters dramatically reduces PM2.5 concentrations in the Dean's Suite when it is activated, even on medium flow setting.
Read 6 tweets
Richard Corsi, PhD, PE (Texas) Profile picture
Sep 19
1/ The Dose Makes the (risk of) Infection

My blog entry from August 2020. Still some unknowns at that time, but the fundamentals have not changed.

corsiaq.com/2020/08/19/the…
2/ If you understand that with COVID-19 we have been dealing with an airborne infectious disease for almost 4 years, the concept of inhalation dose & key parameters that define it provides a roadmap for dramatically reducing infections.
3/ Unfortunately, the roadmap was never used (or used late and without significant clarity) by authorities charged w/ oversight of pandemic reduction, and has now been effectively shredded.
Read 5 tweets
Richard Corsi, PhD, PE (Texas) Profile picture
Sep 11
1/ On the morning of 9/11 my wife & I like so many others were shocked & horrified. My wife reminded me this morning that on that day I was emphatic that large numbers of people would also get sick and die from ...
2/ extraordinary inhalation, dermal, & hand-to-mouth exposure to dust from fallen WTC towers & combustion products thereafter. Cement dust, asbestos, toxic metals, plasticizers, flame retardants, products of jet fuel combustion, products of smoldering building materials, & more.
3a/ This was obvious to Dr. Paul Lioy & colleagues of EOHSI/Rutgers who went to the scene to collect dust samples. They "scooped it from the windshields of nearby cars and secured it in Teflon bags" for laboratory analyses.
Read 10 tweets

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