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Injury or death due from Oxygen deficiency is a relatively common occurrence
in the Process Industries, Refining, Power, Manufacturing and Sewage
Collection. Rescuer deaths account for more than half of these fatalities.
Asphyxiation is the leading cause of death in industrial accidents every year.
How long can you hold your breath? Most people answer a minute or so. When
air is inhaled, Oxygen enters our blood stream by passing through lung tissue,
called alveoli, from the air on one side into blood on the other side.
This works because the partial pressure of Oxygen is higher on the air side
than on the blood side.
If you enter an area with little or no Oxygen, the results can be deadly.
Oxygen now passes through your lung tissue as before, but out of your
bloodstream and into the Oxygen deficient atmosphere! Several breaths and you
go down. Unfortunately, humans cannot sense a reduced Oxygen level.
Portable instruments are the standard for confined space entry and
are used by teams of people to sample and enter sewers, tanks, pits and
other such locations. However, in areas where the public, workers or performers
are often present, such as in power plants, manufacturing, entertainment,
healthcare, food or beverage operations, fixed gas detection is usually the low
cost, highly effective solution for personnel protection and loss prevention. Installed
fixed gas detection continuously monitors the hazard at critical locations,
even away from the workers, performs supervisory notification, has local
annunciation as needed and does not require human presence to warn of a
hazardous condition!
In many common work environments, there is the potential for Oxygen
deficient atmospheres caused by exposure to bottled and cryogenic gases.
Cryogenic liquids have huge expansion ratios (460 - 840 to 1 for those listed)
so a large gas cloud from a small amount of cryogenic liquid is probable. The
presence of a cryogenic gas in a manufacturing facility is usually indicated by
the tall white tank(s) outside the building. Continuous monitoring with hazard
mitigation measures must be employed to insure the safety of personnel working
in the area of gas use or storage.
When placing fixed gas detection, it’s useful to understand the hazardous
Gas dynamics such as, ventilation (HVAC), potential stratification or diffusion
and the physical properties of the gas. Simple smoke tests can reveal essential
air flow characteristics of the area and greatly simplify gas detection
placement. Sensor elevation is a frequent question and the answer is
deceptively simple. Mount sensors in the breathing zone (4-6 feet above grade)
for personnel protection. Caution: Lighter than air gases can produce false
safe readings on a conventional Oxygen sensor. These applications require a
Membrane O2 sensor.
Soft drink bottling, Beer, Wine and Distilled Beverages all use or generate
CO2. Cryogenic freezing employs liquid CO2 or N2 as does human blood, egg,
sperm and tissue storage. Inert welding processes use Argon. Performance venues
generating fog or smoke have Dry Ice (frozen CO2) or liquid N2. Environmental
chambers and test cells inject liquid Nitrogen or use heat exchangers for rapid
cooling. Hydrogen is used extensively in alternate fuel vehicle research.
Liquid Helium cools superconducting magnets for Research activities and medical
imaging such as MRI machines. And don’t forget the very common but
hazardous instrument shelter which has bottled gases, product streams, and
perhaps flue gas piped inside!
There are literally hundreds of situations where workers, even the public,
can be exposed to Oxygen deficiency conditions. Some of these are potentially
fatal. Beyond the obvious permit required or regular confined space
applications, workers pass through, visit or work every day in areas with
hazards capable of producing dangerously low levels of Oxygen. In frequent
or continuously occupied areas, fixed gas detection is the most effective and
lowest cost solution.
OSHA 29 CFR 1910.146, Permit Required Confined Space
Alarm notification to a remote location, manned 24/7/365 and capable of
response
Common Cryogenic gases include Nitrogen, Carbon Dioxide, Helium, Argon,
and Hydrogen
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