CARO Refrigerant Properties and Safety 2

Question 1

Under ASHRAE Standard 34, what safety classification is assigned to ammonia (R-717)?

Accepted Answer

B2L

Answer

Ammonia has higher toxicity (B) and lower flammability with a slow burning velocity (2L), so it is classified B2L.

Question 2

Compared to air, ammonia vapor at room temperature is:

Accepted Answer

About 60% as dense, so it tends to rise

Answer

Ammonia's molecular weight of about 17 versus air's roughly 29 makes dry ammonia vapor lighter than air.

Question 3

What is the NIOSH Immediately Dangerous to Life or Health (IDLH) concentration for ammonia?

Accepted Answer

300 ppm

Answer

NIOSH sets the ammonia IDLH at 300 ppm.

Question 4

At atmospheric pressure, anhydrous ammonia boils at approximately:

Accepted Answer

-28°F

Answer

Ammonia's normal boiling point is about -28°F (-33°C), which is why spilled liquid flashes rapidly.

Question 5

Which metal must NOT be used in contact with ammonia in a refrigeration system?

Accepted Answer

Copper and brass

Answer

Ammonia, especially with any moisture present, attacks copper and copper alloys such as brass.

CARO - Certified Assistant Refrigeration Operator Practice Test