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AirQ Profile picture
AirQ
@AirQ007
Put a stop to airborne infections. Clean air is everyone’s right.
Apr 1, 2021 • 12 tweets • 4 min read
With teachers afraid for their own safety (despite assurances otherwise) it should come as no surprise that 20-24% are choosing not to work in what they believe are high risk conditions. hwdsb.on.ca/wp-content/upl… (1/n) In a recent TDSB survey 80% of teachers reported not feeling safe at work. 70% could not access to tools/resources for their job. And only 30% cited trust between employees and management. tdsb.on.ca/Portals/0/docs… Let’s be clear: This is a crisis. This is unsustainable... (2/n)
Mar 31, 2021 • 11 tweets • 5 min read
Indoor measurements have convinced me that our model of how this virus spreads is incorrect. We understand superspreading events, and we also see the impact of close contacts of long duration. But there’s a third type of transmission: let’s call it the “stray bullet” (1/n) Big box stores, factories etc, have a large volume of mixed air w/ many occupants. Measurement in large open spaces show breath is diluted rapidly. We released a large amount of CO2 in one such space: it dispersed at equivalent 16 ACH. Affecting all sensors in 1min45sec. (2/n)
Mar 21, 2021 • 7 tweets • 3 min read
Many experts recommend NDIR sensors for sensing CO2. But what exactly is NDIR sensing anyway? And what are the other technologies that we might use to sense CO2 in future? Let’s explore this in a short thread... (1/n) Fortunately air is transparent. Otherwise we wouldn’t be able to see a thing: it’d all be a smoky haze. But this isn’t true at wavelengths invisible to us. At other frequencies, gases are opaque, & look like smoke in the air. Here’s a chart of these “smoky” wavelengths. (2/n)
Mar 6, 2021 • 12 tweets • 5 min read
Saturday morning is a great time for a thread on how to calibrate your CO2 meter. Why Saturday morning? Because we calibrate to ambient CO2 levels in outdoor air. And on Saturday mornings it’s lower than other days/times since there’s less traffic around. Let’s get started! (1/n) So, how do you know if your CO2 meter needs calibration in the first place? The easiest way to check is to take a reading outside. If less than 400ppm that’s below global ambient. For that check Mauna Loa Observatory in Hawaii esrl.noaa.gov/gmd/ccgg/trend… (today it’s 416.75 ppm)(2/n) Image
Feb 21, 2021 • 4 tweets • 1 min read
Exactly one year ago I was quite concerned about a new emerging virus. So I created a Facebook group to share practical fact-based info about it. This was one of the first posts on Feb 21, 2020: “This image below is the most important part of the daily WHO updates...” (1/n) “...It’s the chart of number of international cases outside of China, and we’d like to see it start trending down. At first (on left), we see that almost all cases were from China (orange), then over time, the growth was from cruise ship cases (blue), and now it’s...” (2/n)
Feb 18, 2021 • 4 tweets • 1 min read
Today one of my kids took a CO2 meter to class. They said it was hard to see if windows were opened a crack or not, but here’s the chart: Image The dip in the middle is when they left for a short break.
Feb 12, 2021 • 15 tweets • 6 min read
(1/n) Given recent funding directed to the use of plexiglass barriers for fighting COVID-19, I thought a thread on what experts have said on the topic would be helpful... (2/n)According to @kprather88 they block big droplets but aerosols float right around them