Which of the following describes the function of the inner wall in a type "B" vent?

The function of the inner wall in a type "B" vent is primarily to protect against corrosion. This is essential because type "B" vents are commonly used for the flue gases produced by gas-fired appliances. The nature of these flue gases, combined with moisture and possible condensates, can lead to corrosive conditions.

Therefore, the inner wall is typically constructed from materials that are resistant to corrosion, ensuring that the vent remains functional and safe over time. This contributes to the overall longevity and reliability of the venting system, allowing it to effectively expel exhaust gases without degrading due to chemical reactions that can occur in the presence of moisture and combustion byproducts.

Other functions, such as providing structural support or insulating the outer wall, may be relevant to the design of the vent system, but they are not the primary purpose of the inner wall. Similarly, while minimizing heat loss is important in many heating systems, in the context of type "B" vents, the inner wall's primary role does not directly pertain to heat retention but rather to mitigating the effects of corrosion.