Chimney Safety Institute of America (CSIA) Certification Practice Test

A progressive decrease in draft indicates what issue?

1. Improper ventilation

2. Development of blockage in the flue

3. Excessive heat buildup

4. Problems with fuel quality

The correct answer is: Development of blockage in the flue

A progressive decrease in draft in a chimney or flue system typically indicates the development of blockage. Draft is the natural flow of air that moves combustion gases from inside the appliance up through the flue, and a blockage can disrupt this flow. When there is a gradual reduction in draft, it often suggests that something, such as soot, creosote buildup, or even a foreign object, is obstructing the flue, which hinders the efficiency of venting exhaust gases. In contrast, improper ventilation may lead to other issues, but it wouldn’t necessarily be indicated by a gradual decrease in draft. Excessive heat buildup typically relates to different scenarios, often indicating something else entirely, such as the potential for hazardous conditions, rather than just a decrease in draft. Similarly, problems with fuel quality affect combustion efficiency and emissions but are separate phenomena not directly linked to draft measurements. Therefore, the progressive decrease in draft is most closely associated with the developing blockage in the flue.