1/ Done looking at data for last few days and on-off experiments for today. Effectiveness = fractional reduction of PM2.5 with CR-Box on vs. before switched on (no control). With CR-Box on highest flow the effectiveness is greater than 0.98 (PM2.5 drops to < 2% of initial).
2/ In terms of background aerosol concentrations in shared air, that's like wearing an N95 mask.
On lowest flow the effectiveness is 0.79 (PM2.5 concentration drops to 21% of pre-control level. Still not bad!
3/ We normally keep the system on mid-flow (experimental design) and it activates at 8 a.m. and switches off at 5 p.m. each day. Looking back at the past few days it appears that on mid-flow we push or exceed a 90% reduction.
4/ The Dean's Office suite has a central core, four offices, and a conference room. We generally keep all of the interior doors closed and the CR Box is in the central core, which also includes a door that is opens occasionally into a busy lounge where students study.
5/ PM2.5 concentrations always increase when the door is opened. The total suite floor area is approximately 1,000 ft2 (maybe a tad more) and the central core around 375 ft2 (by recall - measured previously and I know this is close).
6/ Upshot - The #CorsiRosenthalBox in the Dean's suite @UCDavisCOE is substantially reducing occupant exposures to fine particulate matter - including respiratory aerosols.
7/ Experiments will continue for 6 to 9 months with intermittent testing in a chamber to compare against initial metrics - CADR*, single-pass removal fraction*, pressure drop, power consumption, dB, all as a function of flow setting. * distinguished by particle size.
8/ Several other CR-Boxes on campus also being studied. Proud to be part of this great team = @CappaSnappa, Theresa Pistochini, Graham Jaeger. Theresa and Graham are doing the heavy lifting!
9/ And of course, thanks to our other very hard working colleague .........
• • •
Missing some Tweet in this thread? You can try to
force a refresh
We are doing long-term measurements of CR Box performance in a number of real occupied environments @ucdavis, with intermittent (every 2 months) take-down and detailed lab analysis. Here are results for one office suite.
2/ The CR box is programmed to switch on at medium setting at 8 a.m. each morning and switch back off at 5 p.m. On occasion it gets switched off and back on during the occupied day to ascertain response. The plot above shows 10-min averaged PM2.5 concentrations.
3/ 1 = previous occupied day end and response when CR Box switches off; 2 = CR box activation at 8 a.m. on July 20th; 3 = CR box intentionally switched off at approx 2 p.m.; 4 =CR box switched back on at high flow setting at approx 4 p.m.; 5 = CR Box switched off at 5 p.m.
NG stoves is a hot issue. There is abundant & increasing literature related to NOx emissions, & impacts on health & climate change associated w/ natural gas combustion. This thread focuses only on particle emissions from gas stoves.
2/ Cooking with natural gas, including stove burners and ovens, leads to emissions of ultrafine particles (UFP).
3/ Fuel type (methane, natural gas, odorant-free natural gas), level of primary aeration, mixture flow rate, and fuel sulfur content are factors that can impact the amount and nature of particle emissions.
1/ #Incense Burning
Incense use in the US is increasing. In 2018, the US incense market size was $128 M USD & is forecast to reach $281 M by 2025.
2/ Incense comes in various forms - sticks (common in the US), Joss sticks, cones, coils, rope, powders, and smudge. Numerous health impacts of exposure to incense smoke have been reported. For example, ...
3/ Cognitive effects, particularly on older adults who burn incense, have been observed. The genotoxicity of certain incense smoke condensates in mammalian cells have been observed to be higher than tobacco smoke condensates.
1/ New CDC recommendation on ventilation - as equivalent ACH (eACH). Aim for at least 5 air changes each hour and upgrade to MERV-13 filters. More thoughts below.
2/ It's a good start and should decrease inhalation dose of respiratory aerosol concentrations by between about 20% to 40% in many classrooms (based on my experience w/ typical starting points in schools --some w/ recirculation through MERV-13 filters already achieve 5 eACH).
3/ Importantly, it is NOT difficult to achieve MUCH higher than 5 ACH in classrooms - even approaching 10 equivalent ACH w/ ASHRAE 62.1 ventilation + a #CorsiRosenthalBox, or 6 ACH w/ 62.1 in a typical classroom & a good HEPA air cleaner.
Efficiency vs. Effectiveness - They are Not the Same
Over the past 3+ years there has been a sharp rise in interest related to indoor air cleaners. I have consistently seen confusion over the terms efficiency and effectiveness. This thread is about the difference. 1/
When thinking about air cleaners, make sure not to conflate efficiency and effectiveness.
An air cleaner that is intended to remove aerosol particles from indoor air can be close to 100% efficient at removing particles as they flow through the device. 2/
That sounds great, right? Maybe. Maybe not. In fact, a device that is 100% efficient (captures all particles that move though it) may be highly ineffective. What? How can this be? 3/
1/ Challenged by some as to why I am wearing a mask in this video if the CR Box works so well. First, I wear an N95 mask in all indoor shared spaces at work. I do not apologize to anyone for that.
2/ For the size of the dean's suite & level of ventilation, this single CR box reduces our inhalation dose of respiratory and other aerosol particles by roughly 50% on high setting. That's good, but not nearly the dose reduction achieved by wearing a well-fit N95 mask.
3/ An N95 mask yields at least a 1 in 20 (95%) reduction in inhalation dose of virus-laden respiratory aerosol particles (and higher for particles of the size most relevant to conveyance of SARS-CoV-2).