An oxygen monitor is used to decide whether a chiller machine room is safe to enter after a refrigerant release. Below what oxygen reading is the atmosphere treated as oxygen deficient?
Correct Answer
B) Below nineteen and a half percent oxygen by volume
Ordinary air is about twenty-one percent oxygen, and an atmosphere is treated as oxygen deficient once it falls below nineteen and a half percent. That threshold is deliberately conservative, because judgment and coordination start to suffer well before a person notices anything is wrong. Refrigerant vapor does not poison the air so much as push the oxygen out of it, and a large release in a poorly ventilated machine room can do that quickly and without warning.
Why This Is the Correct Answer
Nineteen and a half percent is the line at which an atmosphere is considered deficient and unsafe to enter without supplied air. It sits only a percentage point and a half below normal because the effects of low oxygen come on gradually and are not obvious to the person experiencing them. Anything below it means ventilate and re-test, or enter with supplied air.
Why the Other Options Are Wrong
Option A: Below twenty-one percent oxygen by volume
Twenty-one percent is normal air. Treating any reading below normal as deficient would put a room out of service for a trivial fluctuation.
Option C: Below sixteen percent oxygen by volume
Sixteen percent is well into the range where judgment and coordination are already impaired. Waiting for that reading means people are affected before the alarm means anything.
Option D: Below twelve percent oxygen by volume
Twelve percent is close to the level at which a person collapses. No usable warning threshold sits that low.
Memory Technique
Twenty-one normal, nineteen and a half is the line. Barely a point and a half of margin, which is why it is taken seriously.
Reference Hint
An atmosphere below nineteen and a half percent oxygen by volume is oxygen deficient and unsafe to enter without supplied air.
More epa-608-type-3 Questions
Some jobs on a chiller count as a major repair under the refrigerant rules, which changes what a technician is allowed to do with a badly leaking machine. Which job falls into that category?
An owner asks how many pounds of refrigerant the rules allow to be left inside a chiller once the recovery has been signed off. What is the correct answer to give him?
The motor of a hermetic centrifugal chiller sits inside the pressure boundary rather than outside it on a shaft. What follows from that construction?
A low-pressure chiller's rupture disc has a discharge line running from it. Where does that line have to terminate?
A refrigerant vapor detector in a chiller machine room reaches its alarm level. Besides sounding, what is that alarm expected to do?
Which piece of equipment requires a technician to hold Type III certification before it may be serviced?
What property of the refrigerant is what actually places an appliance into the low-pressure category?
During normal operation, what condition exists inside the evaporator of a running low-pressure centrifugal chiller?
In what unit is the required final recovery vacuum for a low-pressure appliance normally expressed?
What should a technician do about the water in the chiller tubes before pulling a deep vacuum on the machine?
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