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Nitrogen oxides NOx
These oxides cause acid rain, which gives both acidified lakes and
algal blooms in eutrophic waters.
High concentrations may cause respiratory
diseases.
Hydrocarbons (HC)
A large group of substances all contain both carbon and hydrogen.
It is the hydrocarbons, which make exhaust
fumes smells bad.
They causes cancer and contribute to the
formation of ground-level ozone.
Tropospheric Ozone
Ozone is not found in car exhaust fumes, but is formed when the
vehicle´s exhaust emissions of hydrocarbons and nitrogen dioxide
react with sunlight.
Ozone act as a useful UV filters in the
atmosphere, but near the surface, it is harmful to all living
creatures. High concentrations of ozone in the
breathing air can lead to reduced lung function and increased risk
of infection.
Gas monitoring and demand controlled
ventilation in garages and parking garages
Nitrogen dioxide NO2 is
formed in bus- and truck garages, road tunnels, mountain cavities,
etc.
Gas monitoring in garages meet two main
needs:
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To warn when the quantity of harmful gases
reaches an unhealthy level.
-
To ensure that the management of
ventilation is done the best and most profitable way, ie.
according to fresh air requirements.
When the concentration becomes too high, the
fans starts automatically and stops again when the NO2 concentration
has down to the predetermined level.
Harmful gases
Harmful amounts of nitrogen oxides (NOx), hydrocarbons (HC) and
carbon monoxide (CO) can be obtained from petrol and diesel exhaust
fumes. As a rule only carbon monoxide is
monitored in the garage since it is often wrongly believed that the
other gases do not reach harmful levels.
Carbon monoxide is an extremely dangerous
toxic gas. Earlier, people often commited
suicide by inhaling exhaust fumes from cars.
Today, the concentrations are much lower,
thanks to catalytic converters in cars and carbon monoxide is no
longer an environmental problem, except perhaps at cold starts.
Regarding carbon monoxide from a gas
monitoring point of view, it is appropriate to have two alarm
levels, one of which occurs at 35-50 ppm (CO / resp 1-2 ppm
(NO2), and the second at about 70 ppm or 5 ppm.
Hygienic threshold limit values for NO2 (gaser from diesel
vehicles, propane driven ice makers).
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NGV = 1 ppm om källan är avgaser: Varning, fläkt startar eller går
från halv till helfart
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TGV = 5 ppm: Larm, takgränsvärdeWith NGV is
understood a concentration that is acceptable for a full day (8
hours).
TGV is the concentration of the average value
during 15 minutes of carbon monoxide level / nitrogen dioxide level.
The alarm level is exceeded in two gas
sensors simultaneously for the warning lights to be activated.
At the higher alert level, for example, on a
juice blender warns of unhealthy levels of carbon monoxide /
nitrogen dioxide levels, it is advisable to have exceeded the higher
of two gas sensors simultaneously for juice blender to be activated.
The reason is to avoid the "distorting load"
it can give rise to if a car happens to be in direct proximity to a
sensor resulting in of an overdose of carbon monoxide or nitrogen
dioxide.
A sensor density of at least 1 sensor /
400-500m2 is appropriate.
If there is heavy traffic in the garage, it
is important to take account of other harmful gases Nox (collective
term for various nitrogen oxide compounds) and hydrocarbons.
In similar cases specific CO and NO2 sensors
cannot cover the need for detection. Other sensors are required that
can detect these gases.
Ventilation control
The minimum requirement to for ventilation control is that the gas
monitoring facility affects ventilation in such a way that if there
is harmful gas the fresh air intake should increase enough for the
gas concentration to be reduced to harmless levels.
A well-regulated demand controlled
ventilation in a garage not only improves the air quality but also
minimizes energy consumption by avoiding unnecessary ventilation.
If you optimize ventilation according to the
gas concentration it is enough to ventilate when the air is bad.
With a modern gas monitoring plant you can
obtain not only alarm functions (two levels) but also control
functions for air evacuation.
NO2 alarm in ice rinks
In the case of ice rinks where the nitrogen dioxide may occur at the
incomplete combustion of LPG-powered ice-makers and thus cause
health-damaging concentrations, it is recommended that a detector be
placed at either short ends of the rink diagonally from each other
to get the best coverage.
See also Projecting Guide
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