1/ Don't be fooled by some air cleaning companies that claim their device is highly efficient. When claims are made about removing 95% or 99% of particles from air, this nearly always refers to % of particles removed THAT FLOW THROUGH THE DEVICE (single pass removal efficiency).
2/ A device can be 99.5% efficient & highly INEFFECTIVE if it has little flow moving through it. The product of fractional removal efficiency (max = 1.0) & volumetric flow rate (e.g. cubic feet per minute) is the important parameter (& known as CADR or Clean Air Delivery Rate).
3/ Example - Company for device 1 claims it removes 99.5% of particles from air (fractional single-pass removal efficiency = 0.995), but the device moves only 30 cfm of air (CADR = 0.995 x 30 cfm = 30 cfm).
4/ Device 2 removes only 60% of aerosol particles from air (fractional removal efficiency = 0.60) but moves 500 cfm of air (CADR = 0.6 x 500 cfm = 300 cfm). In this case, I want the far less efficient device, which is actually far more effective for particle removal from air.
5/ Be effective. Just do it!

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More from @CorsIAQ

19 Sep
1/ Inhalation Dose
It's been about inhalation dose from day 1. We have not kept our eye on the ball. Critical pre-vaccination. Critical post-vaccination. Been writing & speaking about this for nearly 20 mos. Reducing inhalation dose is a must. Come on folks, just do it!
2/ Reducing Inhalation dose using layered interventions is still important, whether unvaccinated or vaccinated (breakthrough cases), in close contact (near field) or far field in the same indoor space, in a car or classroom, in a restaurant or apartment, young or old.
3/ Inhalation dose associated with virus laden aerosol particles is defined by the same variables (whether close contact or far field ---- don't bicker about one or the other - I've previously tweeted about this):

Dose(inhal,i) = C(i) x B x t x fdep(i)
Read 25 tweets
13 Sep
1/ I am really looking forward to meeting new students and helping new College of Engineering students to moove into their dorm rooms later this week.
2/ My message will be clear. Stay safe. Stay focused. Learn the fundamental principles and tools of your trade as you will be able to use these to change society for the better and to help heal the planet.
3/ While you are in college, take advantage of being on such a great campus. Join student groups & get to know faculty and staff. Ask for help when you need it. We are a community and are here for each other.
Read 5 tweets
5 Sep
1/ As a follow-up to my earlier email ....
First, the concentrations of ozone needed to disinfect indoor surfaces is significant and approach or exceed the IDLH (Immediately Dangerous to Life or Health) level. So, use of ozone should be done w/ great care, if done at all.
2/ Ozone (O3) is a moderate oxidant. It reacts with almost all indoor materials, some more than others, as well as oils that we add to or unknowingly leave behind (e.g., skin oils) on those surfaces.
3/ These reactions can (over time), lead to material degradation, e.g., brittleness of rubber seals, leaching of lead from lead-based paints, and even increased susceptibility of some materials to mold growth (research done in collaboration w/ @KerryKinney14 @ut_caee ).
Read 16 tweets
4 Sep
1/ I hope that we have collectively learned a lot (a very long list) from this pandemic. I fear that many have not.
2/ The overwhelming obvious: Vaccines reduce risk of hospitalization and death. Reducing inhalation dose of virus-laden aerosol particles reduces risk of infection, hospitalization and death.
3/ Masks, increased ventilation, appropriate filtration all reduce inhalation dose, and therefore are important weapons in reducing risk of infection, hospitalization and death.
Read 11 tweets
3 Sep
1/ Tomorrow is my last day @Portland_State. Will miss wonderful dean colleagues, as well as faculty, staff, & students of the Maseeh College of Engineering & Computer Science @MCECSpdx. We accomplished much TOGETHER these past 3 yrs. #ThinkBoldMCECS! #ShineBrightMCECS! Images .
Some of the most inspiring students you will find anywhere. You are giants!
Incredible @MCECSpdx staff. You rock!
Read 26 tweets
13 Aug
1/ SARS-CoV-2 travels in aerosol particles emitted from an infected individual. You want to reduce the amount of these particles you breathe (lower inhalation dose is important). We know from decades of research that the following lower your inhalation dose of aerosol particles.
2/ Masks: The higher the quality and better the fit the less aerosol particles you inhale that came out of the respiratory system of an infected person. No rocket science here.
3/ Ventilation: The greater the amount of ventilation the lower the aerosol particle concentration that originated from an infected individual(s) in the air of indoor spaces. That means you will inhale less. No rocket science here.
Read 8 tweets

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