Chimney Safety Institute of America (CSIA) Certification Practice Test

Which stainless steel alloy is recommended for gas appliances expected to condense?

1. 304

2. 316

3. AL 294-C

4. AL 202

The correct answer is: AL 294-C

The recommended stainless steel alloy for gas appliances that are expected to condense is AL 294-C. This alloy is specifically designed to withstand the corrosive effects of condensing flue gases, which can be highly acidic. The composition of AL 294-C provides superior resistance to pitting and crevice corrosion that can occur in environments where condensation is present. In contrast, 304 and 316 stainless steel alloys, while they have good corrosion resistance for many applications, may not provide the same level of protection against the specific corrosive conditions associated with condensation. 304 is often used in less harsh environments, while 316 offers improved resistance due to its addition of molybdenum but is still not as effective as AL 294-C in handling the acidic condensate produced by gas appliances. AL 202 is not typically used for flue gas applications and does not provide the same level of resistance to corrosion from acidic conditions. Thus, AL 294-C stands out as the most suitable choice for gas appliances that can produce condensate, ensuring longevity and safety in their operation.