‘A man has been rushed to hospital after a truck carrying human waste exploded in WA’s south.’

‘Nearby workers told Seven News the explosion was big enough to rock their building, before they rushed to help the man.’
‘It remains unclear what caused the truck to explode, but according to Seven News, authorities say it had something to do with the gases inside the truck.’
Does everyone remember this, it happened recently in early March. This has got me thinking about sewer gases and the harm they can potentially cause.

So, what is sewer gases, what is in it?

Sewer gases are typically made up of, hydrogen sulfide, ammonia, methane, esters, carbon monoxide, sulfur dioxide and nitrogen oxides. Sewer gases are created by the decomposition of organic household and industrial wastes by anaerobic bacteria breaking the material down. These gases are all odorless apart from hydrogen sulfide and ammonia. Its these two gases that give you that sewage smell we all know like a rotten egg smell.

Can sewer gases be harmful?

They are a cause for concern due to their odor, health effects and potential to cause fire or explosions.
“Although hydrogen sulfide is a toxic gas, it will not harm people at the concentrations that exist in a house with sewer gas odor problems. Studies have shown that hydrogen sulfide has a depressant effect on the central nervous system in concentrations above 150 ppm. This is 15,000 to 150,000 times the amount detectable by most people. Not enough gas is generated in the sewers for concentrations to approach the dangerous level in the dwelling.”

However, if a person were to enter a tunnel or deep hole that contained sewage undergoing anaerobic breakdown, there is a chance they could be overcome by Hydrogen Sulfide poisoning.

Here’s an example of an incident in ‘Dublin 2015’.
“Two brothers who were killed after they were overcome by fumes while working in an underground sewer died of hypoxia due to toxic levels of hydrogen sulphide, an inquest has found.
Brothers Alan (45) and Stephen (32) Harris were working on a sewage drain at Drumnigh Woods estate in Portmarnock, Co Dublin when the accident occurred last June.
Alan Harris of Hazelbury Park, Clonee, Dublin 15, died at Beaumont Hospital on June 10th. His brother Stephen Harris of Monasterboice Road, Crumlin, Dublin 12, died two days later.
Both men died as a result of hypoxia, secondary to exposure to toxic concentrations of hydrogen sulphide, Dublin Coroner’s Court heard on Tuesday.”

If exposed to very high concentrations of sewer gas, a person can asphyxiate and die. More common symptoms of exposure to sewer gas include nausea, eye irritation, and difficulty breathing. Different symptoms are displayed, as gas concentrations increase to greater than 700ppm, which can be fatal.

Methane and hydrogen sulfide are highly explosive gases that are produced in sewer gas and can be ignited by possible flames and sparks. There are a number of cases and examples over the years of explosions caused by these gases. The below clip show’s the explosive power associated with sewer gases. https://www.youtube.com/watch?v=kjAx37HtaRE

So yes, sewer gases can be harmful in confined and high concentration area’s but a slight sewer smell within a home, (an indication of a blockage somewhere), is not immediately detrimental to your health.

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