Vermont Natural Gas Certification Practice Test 2025 – Your Comprehensive All-in-One Guide to Exam Success!

The restriction imposed by corrugated chimney liners on the capacity of Type B gas vents is 20%. This percentage is significant because corrugated chimney liners can create additional friction and turbulence within the venting system, which can reduce the effective capacity that is available for venting combustion gases.

In practical applications, these liners can cause the gas vent to be less efficient, which means that the system must be designed considering this reduction in capacity to ensure safe and effective venting. Understanding this restriction is crucial for anyone involved in the installation and maintenance of gas venting systems, as it helps to prevent issues such as improper venting, which can lead to dangerous conditions like backdrafting of combustion gases.

The other percentages listed do not accurately represent the standard industry understanding of how much capacity is typically restricted by the use of corrugated liners, making 20% the correct and necessary adjustment to the venting capacity in this context.