Tag Archives: air

Today there was a fire in a WMATA subway tunnel near L’Enfant. The National Transportation Safety Board (NTSB) is now investigating, and I have confidence that they will do a thorough investigation. I have some questions about actions taken right after the smoke was reported that no one, or at least no one in the media I have seen, has asked. The station filled with smoke, and they evacuated it. WMATA stopped running green and yellow trains through L’Enfant. However they kept running blue, orange, and silver trains through, but these trains did not stop at the station, as they normally would. For those not familiar with L’Enfant Plaza Metro Station, orange, blue, and silver lines share the same track on the lower level, and yellow and green share the same track on the upper level. My question is, were they sure it was safe to keep sending the orange, blue, and silver trains through? I am not asking from the standpoint of the fire, because presumably, they traced the location of the smoke enough to know it was not in the lower tunnel. By safe, I mean because of the potential inhalation of smoke in the lower level tunnels. If the station filled with enough smoke that it needed to be evacuated, then how were they sure that smoke would not enter the trains running through it?

A couple of quick points:

• Just because air smells bad doesn’t necessarily mean it is toxic or hazardous, but conversely, just because air smells fine doesn’t mean it is safe.
• Particulate matter in air and/or smoke is in general not something you really want to breath, but there are different levels of toxicity associated with it. That is, some particulate matter is not more than just an irritant. However, the effect particulate matter has on a person is also affected by that person’s health. People with respiratory issues are more susceptible to any effects.
• Exposure to hazardous or toxic materials can cause effects on different time scales. People who were trapped on the WMATA train in the tunnel, would have acute (short-term) effects from breathing the smoke, such as coughing and having trouble breathing. However, they were probably also exposed to chemicals whose effect is not immediate, such as carcinogens.

The questions I have, that I have not heard anyone ask include:

• What is the air exchange rate between the subway trains and the surrounding air? Can the ventilation be turned off manually, so that there was no air exchange between the train and the surrounding air while the trains were near L’Enfant?
• Were there any measurements taken of the air in L’Enfant, particularly on the lower level where the orange, blue, and silver trains were still running through? If so, what were the measurements of? Just measuring particulate matter will not indicate almost nothing about organic compounds or other chemicals in the air.
• How far did the smoke spread?
• Assuming air measurements were taken, did anyone calculate the amount of contaminants that people in the trains would be exposed to while running through the station based on time and air exchange rate?

My educated guess is that no air measurements were taken. There are probably some sensors in place to measure smoke, but depending on how that measurement is taken, it will tell you information about the particulate matter and that is it. I seriously doubt there was initially any sensors that measured organic compounds or any other type of compounds in the air. I have my doubts that any portable system was put in place during the response. The priority would have been evacuating people (as it should have been). It is possible that WMATA had some qualitative data that there was not much smoke on the lower level. That is, someone may have looked at a video screen and decided the air didn’t look bad. However, unless they had actual quantitative data of what was in the air, then visual assessment of air is a really bad way to make assessments on the quality of the air.

The early statements by WMATA and all other sources, like the fire departments involved, was that they did not know the source of the fire, location or cause. Thus they could not have possibly known what was burning and what would be in the air. For example, if wood is burning, you can expect certain chemicals in the air. If rubber is burning, you can expect different chemicals in the air. WMATA probably decided that the air on the lower level didn’t look that bad, and the trains would go through the station quickly enough that very little exposure would occur. They very well may be right, but with no data and no statements about any calculations, they have no way to prove that. Also, did they inform their passengers of this? If I was on a train, and I knew that the train was going to go through, but not stop, at a station that was filling with smoke, I would get off the train. I don’t feel the need to expose myself unnecessarily to hazardous substances, even if in small amounts. I do not like standing near people who are smoking. The second hand smoke may only minimally increase my risk of disease, but I still don’t see the need for that tiny increase. Thus, was WMATA considering passengers’ exposures at all? Furthermore, did they communicate the possibility of exposure to their passengers on the orange/blue/silver lines to allow their passengers to make their own educated decision about staying on the train? My guess is the answer to both those questions is no, and that is another thing to which WMATA should be made to respond.