Thread by @HuffmanLabDU

A family emergency means I’m flying today for the first time since 2019. Fortunately I’ve got my N95 to reduce my inhaled dose as much as possible + my CO2 meter to gauge air.

Short 🧵 to occupy me while on a layover.

The CO2 was nicely & low in the Shreveport, LA airport (1/x)

2/ On this tiny United commuter flight, 45 minute flight time from Shreveport to Houston, no one with N95 masks. Maybe 2 w/ surgical masks.

Boarding & taxi process, the #AirplaneCO2 briefly peaked at 1600 ppm, but mostly in 1100 range. Obviously higher than ideal, but not bad.

3/ Cruising (if you call it that for just a few minutes) was still in the 1000 - 1200 ppm range. At that upper level, roughly 2% of the air is likely rebreathed from others on board. But the ventilation is also filtering resp. particles from background air relatively frequently.

4/ Kept N95 on tightly the whole flight. Now in Houston and really need food. Fortunately, not too crowded. Did some recon and feel ok taking mask off to eat at this place with low person density & reasonable CO2 at <800 ppm.

5/ I hadn’t planned on this trip to Tucson. Changing plans mid-vacation, leaving family to be with other family. Fortunately we brought a few rapid COVID tests. I took a test immediately before I left the house today. Was negative, obviously. But was glad we had the RATs on hand.

6/ Virtually no one in the Houston airport (or Shreveport) is currently masked. Maybe 1%? Of those, maybe 10% in KN95. Most in cloth or surgical. I’m not sure I’ve seen another N95 (and certainly no elastomeric respirators).

7/ Happily, the CO2 level is very good in the areas I’m wandering in Terminal A of George Bush Intercontinental airport in Houston. Mostly in the 400 - 600 ppm range. But it’s also not very busy. Not sure the take-away there. Consult the airport seers and travel at off times?

8/ CO2 at my gate is a little worse at ~800 ppm, but not bad for a crowd.

I can currently see 63 people at gate. 9 masked. Better than rough airport avg. ~15% here. Of those:

3 below nose 
2 cloth
1 surgical
2 KN95 (parents w/ infant twins)
1 N95 (me)
None on United staff

9/ Short jetway experience was good. Line moving fast, so exhaled air, respiratory aerosols, and CO2 not likely building up much.

10/ Another small plane for second (of two) flights for me today. ERJ175 airplane operated by United. Two seats on each side of aisle in the cheap seats.

Not as lucky with #AirplaneCO2 this round. Very quickly gets to >1600 ppm once I sit down. Not feeling as optimistic here …

11/ They apparently didn’t have time to fuel up the tank. Waiting extra 10 minutes for that. They left the door open & air on. 🙏

CO2 holding steady in the ~1650 ppm range.

I lucked out. No seatmate & behind me is one of the few w/ mask (surgical).

More on the flip side …

12/ CO2 stayed 1700-1900 ppm while on taxi & waiting the few minutes before take off.

Overhead air turned on shortly before take off. More air movement and CO2 at 1400-1600 ppm.

13/ Interesting that @united reworked standard flight attendant speech to announce proud use of “antimicrobial surfaces,” w/ no mention of air filtration already in place. Highlights perceived need to reinforce attention to surface cleaning rather than airborne routes of disease.

14/ Cruising: 1600-1800 ppm range. But in contrast to similar CO2 levels in most indoor spaces, keep in mind that airlines have rapid air exchange. Filtration removes particles (infection worry) while not removing gases. So air is *much* cleaner of particles than w/o filtration.

15/ That said, I’m still leaving my N95 tightly in place for most of flight. I’m taking sips of water & small shovels of gummy bears into my mouth as I quickly dip my mask. It goes back on w/ a quick adjustment as soon as the refreshments are in. It’s comfy enough & I’m fine.

16/ Overall, I’m feeling ok in the experience so far. All travel involves risk, spread of infection as one part. But w/ the air filtration during flight, the moderate CO2 (in my case), and the heavy defense of my N95, I feel reasonably comfortable w/ my personal level of risk.

17/ CO2 dropping as we descend. Started at ~1600 ppm while cruising and steadily dropped to 1100 ppm by landing.

18/ Waiting for Uber outside (in 84 degree F Tucson night time ‘dry heat’). Fortunately, CO2 outside is within range of what you would expect for the sensor (420 ppm +- 30-50 ppm).

19/ And to round it out, the Uber ride was an uneventful 25 min. Driver was masked w/ KN95. Air was on high w/o recirculation. CO2 never got above 660 ppm. 👏

All in all my first set of flights in 30+ mo’s was fairly uneventful. I can’t claim no risk, but I’m comfortable w/ it.

20/ (Postscript) To add some points associated with comments, I want to clarify that this was not intended to be a treatise on best practices of travel or a comprehensive explainer about CO2 & risk. It was a fairly simple live-tweet of some observations I made while traveling.

21/ If you want more detail on CO2 on airplanes or as a proxy for air freshness & ventilation, some quickly gathered threads below

https://twitter.com/joeyfox85/status/1510785191857508357?s=21&t=8eHg7080Vo0s4BEqaGv5OA

https://twitter.com/joeyfox85/status/1545148594289868802?s=21&t=8eHg7080Vo0s4BEqaGv5OA

https://twitter.com/poppendieck/status/1456461078041333760?s=21&t=8eHg7080Vo0s4BEqaGv5OA

https://twitter.com/huffmanlabdu/status/1448335822365728772?s=21&t=8eHg7080Vo0s4BEqaGv5OA

https://twitter.com/huffmanlabdu/status/1447324063613939714?s=21&t=8eHg7080Vo0s4BEqaGv5OA

https://twitter.com/huffmanlabdu/status/1459308113455026178?s=21&t=Go5qdvLrQsVlna6QwE0J-g

22/ And there are many articles that can walk you through different perspectives on the risks involved in air travel. It’s not for me to endorse or summarize here, but to say that you *can* take steps to help assess & reduce your risk while traveling.
washingtonpost.com/travel/tips/fl…

23/ If you are still want more about CO2 or airborne risks, others on Twitter have offered great threads. Some are documented here. Search (Cntrl-F) e.g. for CO2 or airplane on the tabs for media articles or threads. I’m way behind, but still a lot there.
bit.ly/3fzmB16