Test shows Rideau Station air quality OK despite smell

Air quality testing in Rideau Station, the source of a rotten egg smell that causes nausea and headaches for some LRT riders, has only deepened the mystery of what’s wrong in the system’s deepest station.

The testing, done by a professional firm, shows no problems in the station’s air. None at all.

In particular, Buller Crichton Environmental found no trace of hydrogen sulphide gas, which is commonly the source of a rotten egg smell.

The testing was done on a single day, Feb. 6. The Citizen has obtained a copy of the results through an access to information request.

The testing was done at a time when the rotten egg smell was still fairly new. There had been a sewage smell underground, especially at Parliament Station, since the LRT opened.

But the rotten egg reports came later, starting around the beginning of February. Besides making people feel nauseous, the smell raised the possibility of hydrogen sulphide gas, which is toxic to humans if levels go high enough.

Hydrogen sulphide problems are not common in this region. They are often associated with natural gas production in Alberta and Saskatchewan. But the gas can also come from rotting organic matter, and central Ottawa had extensive dumping and burial of waste in the city’s early years. The gas is heavier than air and collects in basements, sewers and other underground spaces.

Besides finding no hydrogen sulphide, the Feb. 6 test found almost none of a wide variety of fumes called volatile organic compounds.

This group includes everything from natural gas and gasoline fumes to glue, paint, paint stripper, pesticides, many cleaning products, and perfumed products.

The test ruled these out. The target level for volatile organics is to keep them under 400 parts per billion in indoor air. The average at Rideau was a mere 1.2 parts per billion. The firm also tested for flammable or explosive fumes and found no trace.

In addition, the oxygen and carbon dioxide levels were good, indicating the station is getting a good supply of fresh air from above ground. And there was no carbon monoxide, indicating no fumes from combustion were leaking into the station.

Testing sites included the platform, two concourses and the Williams Street entrance.

One transit commissioner wonders whether a single day’s testing was enough.

“While I am pleased that the City finally listened to the public’s concerns and tested the air quality in the LRT tunnel, I am disappointed that the testing was limited to one day only,” Sarah Wright-Gilbert said in an email.

“As someone who travels through that tunnel on a twice-daily basis, I can attest that the odour in the tunnel is not always the same intensity. Testing on one day only cannot, in my opinion, provide accurate results. I would like to see RTG and the City perform air quality tests over a period of time to show a range of readings for a more accurate picture, so that the public can be confident that their health and safety is not at risk.”

David Miller, a chemistry professor at Carleton University and a fellow of the American Industrial Hygiene Association, says hydrogen sulphide is a gas that some people can smell even at levels too low for standard instruments to detect. (Skunk spray is another, he said.)

The level they can smell “is much lower than the occupational safety and health guidelines and any reasonable technology a company might use would not detect exposures around the odour threshold of some people,” he wrote. tspears@postmedia.com twitter.com/TomSpears1