Thread by @jljcolorado

1/ Travelling from Colorado to New York City for #ICFUST conference with low-cost air quality sensors.

New: @2b_technologies POM portable ozone monitor.

Semi-outdoors waiting for the bus:

-CO2: 588 (some exhaust)
-PM: 0 (rained yesterday *)
-VOC: 65 (low)
-O3: 15 ppb (**)

2/ Some expl:

@RideRTD Boulder bus station, like a tunnel open on both sides. Modern diesel buses running

- some CO2 from diesels
- Ultrafine PM, low-cost sensors can't see (too small for their lasers)
- Diesels emits very low VOC
- Emit NO, which destroys O3

All checks

3/ @RideRTD airport bus, at the start of 1:15 h trip

- CO2: 944, poor ventilation as usual (likely go up)
- PM: 7, not sure higher than outdoor?
- VOC: 1789, from people, personal care products, bus materials
- O3: 5. From outside, lower bc it reacts w/ people, materials, gases

4/ @RideRTD bus to the airport, halfway through the trip.

Bus is now pretty full. CO2 increasing a lot as usual, not enough ventilation.

The other ones (VOC, PM2.5, O3) are stable

5/ I hope next generation of instruments will combine the best features of these 3 into 1:

- accuracy & great App w/ graphics from @AranetIoT (below)

- cloud storage of @airthings (graphs not great)

- Accurate O3 sensor like @2b_technologies (at much lower cost with mass prod)

6/ I assume VOCs in the bus come from all of those sources: from people's bodies (including O3 reacting with their skin oils), from their personal care products, and from materials in bus etc.

But this sensor is very rough, semi-quantitative at best

7/ E.g. this is one paper in which we looked at the VOC sources in another indoor environment with people, a classroom.

onlinelibrary.wiley.com/doi/10.1111/in…

Btw the great @polsiewski supported this work when she was at @SloanFoundation

8/ I recommend sensors I am traveling with (no conflict of interest)

Some others also work. & many many don't work well. Don't have time to try them all (I wasted a lot of $ testing CO2 sensors in the early pandemic). See what other scientists recommend

9/ Outdoors at the airport near the terminal.

CO2: 570, some exhaust from traffic and planes?
PM: 3, lower than inside bus (did bud have filtration?)
VOC: 311, lower than bus ( normal for outdoor)
O3: 47, typical outdoors

10/ Security line at @DENAirport

- CO2: 964, a bit high, as last time, lots of ppl, not enough ventilation
- PM: 1, lower than outdoor, some filtration
- VOC: 600, not high for indoor
- O3: 0 (within noise). Reacting with tons of ppl, plus lower ventilation

11/ There are indeed VOCs outdoors, but normally a lot lower than indoors, e.g. the measurements I just did, or this paper pubs.acs.org/doi/10.1021/ac…

12/ Train at @DENAirport from main to departure terminal.

- CO2: 1715, very poorly ventilated as in past trips
- PM: 0, so more filtration at least
- VOC: 850, creeping up like CO2, suggests human sources
- O3: 6, higher than expected. Perhaps a VOC interference, perhaps real

13/ Just boarded the 4 h flight to New York with @united

Ventilation NOT yet on, can barely feel any airflow

- CO2: 1640, climbing fast, consistent w/ no ventilation
- PM: 1
- VOC: 376, lower, good
- O3: 2, very low, consistent W/ little ventilation, losses to surfaces & ppl

14/ Way too much for personal use. $6k or so. It is designed for research studies of personal exposure.

But it has very good accuracy, compared w/ cheap electrochemical sensors that don't work at these levels

Trying to talk company into consumer market

15/ Yes, thanks, we often do this in actual research, and the transitions in this thread achieve some of this.

But here I am traveling (and I don't have time for so much of that) so I am just relating my best estimates of what's going on.

16/ In my experience buses are very variable (manufacturer, age, how air is run by the driver etc.). But I agree that they are often very bad

Also high speed trains in Europe (Spain, France) are often very bad.

17/ I was wondering if I could travel with 3 sensors, or if it would be too much to handle

Decided to take them, was all proud the thread was working... till I realized that with the distraction, I forgot my laptop!!

Thankfully @ShellyMBoulder is coming to NYC & bringing it! 🥳

18/ Mid-flight on @united. Was going to work on presentation for #ICFUST, but since I forgot my laptop, can tweet a little more!

- CO2: 1800. High, but stabilized quickly once they turned ventilation on halfway thru boarding
- PM: 0 (filters & started low)
- VOC: 900
- O3: 5

19/ For radon, there are 2 options:

- @airthings, accurate but maddeningly slow for me (24 h rolling average). Also measure other pollutants depending on model

- ecoqube from @EcosenseInc is my favorite. Measures only radon, but fast (1 h) & accurate

20/ Waiting for @lyft at @LGAairport NYC. Parking garage open to outdoors. Very close to planes, taxiing with engines on & cars

- CO2 475 backgr. some combustion emissions
- PM 13 Big city pollution
- VOC 46. Surprising low
- O3 10-50 oscillating. Maybe NO plumes from planes?

21/ @lyft ride to hotel. Toyota Camry, maybe 10 yrs old

- CO2 2500, recirculating ventilation
- PM 6, less than at terminal (losses to ventilation system & filter)
- VOC 2500, usual car smells
- O3: 4, lost to ppl & surfaces, little coming in since no ventilation

22/ I ask the driver to change the recirculated air to outside air. He is confused, after several attempts pushes the button, but recirculation stays on!

Not sure if feature of @Toyota Camry or failure in this one

@lyft & @Uber need to teach drivers about this important detail!

23/ On @lyft, now with open windows (hot)

- CO2 640, much better ventilation through windows ( not fast, lots of traffic)
- PM 15, city pollution coming in
- VOC 676, in-car source, ventilated out like CO2
- O3: 25-33. Coming in, lower due to NO on highway (also in-car losses)

24/ Arrived at hotel in Manhattan.

Ok for now, we will see how it is overnight. Hotel rooms are often poorly ventilated

CO2 600
PM 3
VOC 163
O3 3

25/ Woke up in the morning at hotel

- CO2 1700. Poor ventilation as it seems the norm in US hotels
- PM 12, quite high, not sure why given low ventilation
- VOV 400. Room is spartan, concrete floor, few furnishings, makes some sense
- O3 1, consistent with low ventilation

26/ At #ICFUST conference room in @Columbia Med School

- CO2: 880, ok or a little high
- PM: 5, some pollution coming in w/ ventilation (not good filters in HVAC, despite fancy bldg.)
- VOC 50, very low (surprisingly)
- O3 13, coming from outdoors w/ ventilation along w/ PM

27/ Returning from #ICFUST, ON @Uber to airport.

Looked at CO2, was 5200. I told the driver, he switched off recirculation and quickly went to 800

And he actually ordered an Aranet4 right then while stopped at traffic light!

Uber should be buying a CO2 sensor for each driver!

28/ This is the CO2 graph. From @Uber ride

Went up till I noticed, then went down in 5 min (took pic at start of way down)

If @Uber & @lyft bought CO2 meter for each driver and educated them:
- less driver sick days
- less accidents (CO2 makes you drowsy)
- less sick customers

29 @LGAairport gate

- CO2 1150 not great, worse than @DENAirport
- PM 15, high, maybe outdoor pollution & not great filtration. Or perhaps indoor source not well vented (smells like food from nearby restaurants)
- VOC 146, low for indoors
- O3 very low (consistent w/low vent.)

30/ And another important reason why @Uber and @lyft should give CO2 meters to their drivers.

Indeed I try to avoid these services since the pandemic, but I use them (with an N95 and a CO2 meter) when I really need to.

32/ Boarding on @united.

- CO2 was 750 when I entered plane (10th person to board). Now 1000, climbing
- PM 2, much better than terminal. Ventilation was on when I entered, unlike last 2 flights, filters must be working
- VOC 129, low
- O3 19, from ventilation air

33/ This would be good. I'd be willing to wait longer, pay more for @Uber N95 or @lyft N95 service, w/ driver on N95 & a CO2 monitor.

As would probably the immunocompromised (chemo, transplants) and many others

They have @Uber green, so nor impossible

34/ Taxiing towards takeoff

- CO2 1750, very high as usual
- PM 0, good, filters working
- VOC 270, increased now that everyone on plane (full)
- O3 4, reacting with all the people

35/ Descent towards @DENAirport on @united

- CO2, PM, O3 the same as earlier in the flight
- Curiously VOCs have increased a lot, not sure why. Perhaps just evaporation of personal care products from people.

36/ outside at @DENAirport before boarding bus

- CO2 500, typical, some combustion exhaust (Denver, lots of cars, planes, ground equip.)
- PM 3, low, has been raining which removes it
- VOC 54, low
- VOC 45, typical outdoors summer

We'll see the bus...

37/ Bus to Boulder from @RideRTD.

- better ventilation than other bus rides. I wonder if buses also have an outdoor air vs recirculation setting?

If so @RideRTD needs to educate their drivers, or change the setting to always use substantial outside air, especially when full