Is this the problem that deals with flammability of refrigerants? Although I think ASHRAE 34 goes much more into depth on the subject, the information is also located in the Fundamentals book. Check the index on Refrigerants- Safety Classifications. There is a about 2 paragraphs that discuss this subject and the answer is in there.
The solutions (paricularly NCEES) seem to direct you back to the original source of information vs. another location where it may be mentioned. Make sure you print out the MERM and ASHRAE indexes to help you search faster. I have both in a 3 ring binder; I usually search through the MERM first and then move onto the ASHRAE if I can't find it in MERM. The only time I have had to go outside of these sources so far was for occupancy calculations from ASHRAE 62 to determine ventilation rates.
