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Ozone Environmental
and Health Aspects:
Because ozone has a very
short half-life in aqueous solutions and because the degradation
results in either oxygen or oxygenated by-products, waters treated
with ozone will be less of an environmental hazard than the water
left untreated or treated with halogens or related compounds;
e.g., chlorine.
Because
ozone accelerates the natural oxidation process of both atmospheric
and biological oxygen uptake, water treated with ozone can generally
be recycled in the environment without fear of releasing any toxic
substances.
Ozone
is an acute toxin; meaning its effects upon exposure are immediate,
but short lived. Ozone is not a chronic toxin, and it is not listed
by The American Conference of Governmental Industrial Hygienes
(ACGIH) as a confirmed or suspected human carcinogen.
Although
ozone in the gaseous form is both toxic and corrosive, it presents
no safety or handling problems in properly designed operating
systems. Unlike most other oxidants that are stored on-site in
bulk form, ozone is produced on-site in low concentrations and
immediately consumed. Consequently, any accidental leakage can
be easily controlled, as evidenced by ozone's long safety history
in many applications.
Ozone
gas concentrations in air at less than 5 ppm will be colorless
and have a pungent odor. In concentrations above 5 ppm the gas
has a faint blue color and an unpleasant acrid smell. Breathing
traces of ozone in air for a few minutes is of little public health
concern. The odor threshold of 0.01 ppm is well below the level
of health risks. At 0.1-ppm concentration most people can tolerate
8 hours of exposure. This is the OSHA Threshold Limit Value-Time
Weighted Average (TLV-TWA). At 0.3 ppm concentration exposure
should be limited to 15 minutes. This is the OSHA Threshold Limit
Value-Short Term Exposure Limit (TLV-STEL). Any exposures greater
than 10 ppm should be completely avoided. Even though threat and
lung irritations and edema have been observed after extreme ozone
overexposures, it is important to recognize that during more than
80 years of commercial ozone use, no deaths related to ozone exposure
have ever been reported.
To
prevent a serious exposure, all ozonation systems must comply
with strict safety regulations specified in the Uniform Fire Code
(U.F.C.). These include:
•
Generators in approved gas cabinets or rooms.
• Ventilation of cabinets or rooms and exhaust treatment
to remove any released ozone.
• Monitoring of ozone ambient concentrations at indoor installations.
• Compatibility of all material coming into contact with
ozone.
• Secondary containment and exhaust treatment of all ozone
delivery lines, values, meter, etc. outside of the cabinet.
• External interlocks to turn off the ozone generator in
the event of an external process shutdown.
Ozone:
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Background
Chemical Properties
Ozone Production
Ozone Chemistry
Ozone Environmental and Health Aspects
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