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CONTROLLED ATMOSPHERE (CA) SAFETY CONSIDERATIONS
Air contains nitrogen and oxygen, and only oxygen supports life. Oxygen is normally present at a concentration of
about 21% in the atmosphere. The balance is nitrogen, with traces of other gases.
Controlled atmosphere (CA) systems reduce the oxygen content in the container to 2 -- 5%. These levels will not
support life. The low-oxygen atmosphere is colorless, odorless and tasteless. Indications of a potentially hazardous
situation are generally absent.
One or two breaths in a low-oxygen atmosphere will cause unconsciousness within 10 seconds and death within a few
minutes.
Before entering containers which are equipped with CA systems, the oxygen content must be increased to normal
(21%) by ventilation.
Carrier Transicold containers using the CA option are equipped with:
1. Hazard labels on the front of the unit.
2. Hazard labels near the evaporator access panels. Hazard labels on the evaporator motor mounting bracket.
3. Hazard labels on rear doors of the container.
4. Door interlock system on rear doors of the container to prevent access of personnel when low-oxygen levels are
present.
In addition, a hazard label is provided with the poly sheet curtain, which is used to help stop gas leakage at the rear
doors of the container.
IMMEDIATE EFFECTS OF BREATHING OXYGEN DEFICIENT ATMOSPHERES
As blood passes through the lungs it gives up carbon dioxide and accepts oxygen through the thin walls of tiny air sacs.
--
Blood from the lungs takes less than 10 seconds to reach the brain.
--
Breathing oxygen deficient air flushes the blood of oxygen.
--
The brain is quickly depleted of oxygen resulting in swift unconsciousness.
--
Within 5 seconds of breathing oxygen-free gas, there is a rapid drop of oxygen in the blood. As the oxygen
concentration is progressively lowered the physiological effects are:
Giddiness
S
Mental confusion
S
Loss of judgement
S
Incoordination
S
Weakness
S
Nausea
S
Fainting
S
Death
S
--
Symptoms or warnings are generally absent.
HUMAN RESPONSE TO OXYGEN DEFICIENT ATMOSPHERES
OXYGEN CONTENT OF AIR
15% -- 19%
12% -- 14%
10% -- 12%
8% -- 10%
6% -- 8%
4%
SAFETY SUMMARY
SIGNS/SYMPTOMS OF PERSON AT REST
Decreased ability to work strenuously. May impair coordination and may induce
early symptoms in persons with coronary, pulmonary or circulatory problems.
Respiration deeper, increased pulse rate and impaired coordination, perception
and judgement.
Further increase in rate and depth of respiration, further increase in pulse rate,
performance failure, giddiness, poor judgement, blue lips.
Mental failure, nausea, vomiting, fainting, unconsciousness, ashen face, blue
face.
8 minutes, 100% fatal; 6 minutes, 50% fatal; 4-5 minutes, recovery with treat-
ment for all exposures.
Coma in 40 seconds, convulsions, respiration ceases, death.
Safety--1
T-305
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