A machine room holds chillers charged with R-123, and the vapor monitor has to be set with the refrigerant's exposure limit in mind. What is the manufacturer's allowable exposure limit for R-123 as an eight hour average?
Correct Answer
C) Fifty parts per million, well below the figure that applied to older R-11 machines
R-123 carries an allowable exposure limit of fifty parts per million averaged over an eight hour day, which is far lower than the thousand parts per million associated with R-11, R-12 and R-22. That difference is the whole reason machine rooms holding R-123 machines get vapor monitors, tighter ventilation and more attention to small leaks. A leak that would have been a nuisance on an R-11 machine can put an R-123 room over its limit.
Why This Is the Correct Answer
The allowable exposure limit for R-123 is fifty parts per million as an eight hour time weighted average. It is roughly twenty times more restrictive than the limits associated with the older refrigerants these machines used to hold, which is why the conversion from R-11 to R-123 came with monitoring and ventilation requirements that the original machines never had.
Why the Other Options Are Wrong
Option A: Five parts per million, a limit set for materials handled only in a laboratory
Five parts per million is far more restrictive than the figure for this refrigerant and would make an operating machine room almost impossible to certify.
Option B: Five hundred parts per million, matching the figure used for most halocarbons
Five hundred parts per million is ten times the actual limit and would leave people exposed well beyond what the refrigerant's toxicity supports.
Option D: One thousand parts per million, the same figure that applies to R-11 and to R-22
One thousand parts per million is the figure associated with R-11, R-12 and R-22. Carrying it across to R-123 is exactly the mistake the lower limit exists to prevent.
Memory Technique
Fifty for R-123, a thousand for the old CFCs. The new refrigerant is twenty times fussier about people.
Reference Hint
The allowable exposure limit for R-123 is fifty parts per million as an eight hour time weighted average.
More epa-608-type-3 Questions
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