I got a new toy recently, an Aranet4. It measures CO2 concentration in a given space, which is one way you can get an idea of how well ventilated the space is. This is especially important at the moment given the airborne virus causing the pandemic. Here is a scientific paper from the University of Colorado on the topic for those who have an interest: Carbon dioxide levels reflect COVID-19 risk: Research confirms value of measuring carbon dioxide to estimate infection risk
So with my new toy, I've been recording CO2 concentration in a bunch of different places, especially public transportation. It's interesting to see how buses, ferries, and trains differ. I brought my Aranet4 on the Coast Starlight, Southwest Chief, and the New Mexico Railrunner in December. I figured I'd share here since it's interesting to me, so maybe it is to someone else too!
In a well-ventilated space you can expect 430-500ppm concentration of CO2. 500-1000ppm is likely influenced by the people in the space. 1000+ppm is typically a sign of poor ventilation.
OKJ - LAX on the Coast Starlight in Superliner II Roomette 6
In the measured roomette were two adults, the temperature was set to cold, and the air vent was open.
As you can see, the roomette varied pretty significantly from CO2 1,000ppm to 2,100ppm. Generally, we felt like the room was a tad too warm. What is interesting is that our stop at SLO was from 3:09pm - 3:37pm, which had the door open. I believe that is the cause of the significantly lowered CO2 and improved ventilation for the room. What I didn't expect was that after that point, the CO2 stayed lower for quite a while.
Overall, I think the air exchange in the roomette for this trip is not even close to what Amtrak advertises. They claim air on the trains is exchanged every 4-5 minutes.
LAX - ABQ on the Southwest Chief in Superliner II Bedroom C
In the measure bedroom were two adults, the temperature was set to cold, and the air vent was open.
From the time we boarded until approximately 7am the next day, the air was being exchanged much faster than on the previous train. I don't know if this is because the bedroom is larger with more air coming in, or something else. The room got quite warm in the morning as we approached ABQ. It was also cold outside the train, which may have been a factor for how the HVAC system was operating.
ABQ - Santa Fe on the NM Railrunner Bombardier Bi-Level VI Coach
This train was quite crowded at about 70% load factor at peak. We sat upstairs and were able to have four seats for the two of us.
The ventilation of the Railrunner Bombardiers seems like it did fairly well considering the number of people on board. I would still question the air exchange rates that transit agencies have stated about similar trainsets. Unfortunately, I don't have an Amtrak Superliner Coach recorded to compare.
To me, it seems like it would be really beneficial for Amtrak and Railrunner to install MERV-13 filters and perhaps even UV lights on the HVAC systems. I know in the Bay Area, both BART and SMART have done this and although it doesn't improve ventilation, it cleans the recirculated air. It's pretty clear to me that the amount of air being exchanged from outside the train varies significantly depending on what the HVAC system is doing at any given moment, so if a lot of air is being recirculated, cleaning that air could be beneficial for health.
I will do the return trip as a follow-up post.
So with my new toy, I've been recording CO2 concentration in a bunch of different places, especially public transportation. It's interesting to see how buses, ferries, and trains differ. I brought my Aranet4 on the Coast Starlight, Southwest Chief, and the New Mexico Railrunner in December. I figured I'd share here since it's interesting to me, so maybe it is to someone else too!
In a well-ventilated space you can expect 430-500ppm concentration of CO2. 500-1000ppm is likely influenced by the people in the space. 1000+ppm is typically a sign of poor ventilation.
OKJ - LAX on the Coast Starlight in Superliner II Roomette 6
In the measured roomette were two adults, the temperature was set to cold, and the air vent was open.
As you can see, the roomette varied pretty significantly from CO2 1,000ppm to 2,100ppm. Generally, we felt like the room was a tad too warm. What is interesting is that our stop at SLO was from 3:09pm - 3:37pm, which had the door open. I believe that is the cause of the significantly lowered CO2 and improved ventilation for the room. What I didn't expect was that after that point, the CO2 stayed lower for quite a while.
Overall, I think the air exchange in the roomette for this trip is not even close to what Amtrak advertises. They claim air on the trains is exchanged every 4-5 minutes.
LAX - ABQ on the Southwest Chief in Superliner II Bedroom C
In the measure bedroom were two adults, the temperature was set to cold, and the air vent was open.
From the time we boarded until approximately 7am the next day, the air was being exchanged much faster than on the previous train. I don't know if this is because the bedroom is larger with more air coming in, or something else. The room got quite warm in the morning as we approached ABQ. It was also cold outside the train, which may have been a factor for how the HVAC system was operating.
ABQ - Santa Fe on the NM Railrunner Bombardier Bi-Level VI Coach
This train was quite crowded at about 70% load factor at peak. We sat upstairs and were able to have four seats for the two of us.
The ventilation of the Railrunner Bombardiers seems like it did fairly well considering the number of people on board. I would still question the air exchange rates that transit agencies have stated about similar trainsets. Unfortunately, I don't have an Amtrak Superliner Coach recorded to compare.
To me, it seems like it would be really beneficial for Amtrak and Railrunner to install MERV-13 filters and perhaps even UV lights on the HVAC systems. I know in the Bay Area, both BART and SMART have done this and although it doesn't improve ventilation, it cleans the recirculated air. It's pretty clear to me that the amount of air being exchanged from outside the train varies significantly depending on what the HVAC system is doing at any given moment, so if a lot of air is being recirculated, cleaning that air could be beneficial for health.
I will do the return trip as a follow-up post.
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