What is sewer gas?
Sewer gas is a complex mixture of toxic and non-toxic gases that can be present at varying levels depending upon
the source. It is formed during the decay of household and industrial waste. Highly toxic components of sewer gas include
hydrogen sulfide and ammonia.
Sewer gas also contains methane,
carbon dioxide, sulfur dioxide, and nitrous oxide. In addition, chlorine bleach, industrial solvents, and gasoline are frequently
present in municipal and privately-owned sewage treatment systems.
How are people
exposed to sewer gas?
Sewer gas can enter a home
through a floor drain, from a leaking or blocked plumbing roof vent, or (if the gases are in the soil adjacent to the house)
through cracks in the foundation. Sanitary workers can be exposed to sewer gas during the cleaning and maintenance of
municipal sewers and home septic tanks.
What are the effects of exposure
to sewer gas?
The principal risks and effects
associated with exposure are:
Hydrogen sulfide poisoning. Exposure to low levels of hydrogen
sulfide causes irritation of the eyes and respiratory tract. Other symptoms include nervousness, dizziness, nausea, headache,
and drowsiness. This gas smells like rotten eggs, even at extremely low concentrations. Exposure to high concentrations
can interfere with the sense of smell, making this warning signal unreliable. At extremely high levels, hydrogen sulfide can
cause immediate loss of consciousness and death.
Asphyxiation. High concentrations
of methane in enclosed areas can lead to suffocation as large amounts of methane will decrease the amount of oxygen in the
air. The effects of oxygen deficiency include headache, nausea, dizziness and unconsciousness. At very low oxygen concentrations
(<12%), unconsciousness and death may occur very quickly and without warning. Sewer gas diffuses and mixes with indoor
air, and will be most concentrated where it is entering the home. It can accumulate in basements.
· Explosion and fire. Methane and hydrogen sulfide
are flammable and highly explosive.
How can I avoid being exposed to sewer gas?
· Flush
floor and sink drains with water to prevent the traps in pipes to the sewer from drying out.
·
Occasionally check the roof plumbing vent for blockage from debris such as leaves or bird nests.
- Never enter a
municipal sewer line, septic tank or any other large storage tank without proper training and equipment.
What should I do if I suspect a problem?
First, following the odor, try to locate the point
of entry, such as a basement floor drain. Check for a blocked rooftop plumbing gas vent. By adding water to the
floor drain or removing debris from a roof plumbing stack vent you may be able to prevent sewer gas from entering your home.
In the unlikely event that a leak in gas vent plumbing is behind walls, Precision Locating
can perform a smoke or helium test to find the source, we have the equipment and experience necessary to locate any
sewer gas leak.
Symptoms of headache, nausea, dizziness
or drowsiness may indicate exposure to an odorless gas like methane or carbon monoxide, or to hydrogen sulfide, which smells
of rotten eggs. Persons experiencing severe symptoms should seek immediate medical care.
If you suspect that high concentrations of sewer gas have accumulated in an enclosed space, you should evacuate the
area and contact the fire department for assistance. Avoid creating an ignition source such a spark from an electrical
appliance, match, or cigarette lighter.
