In my line of work, I come across a lot of areas that have a “ventilation system” that intends to reduce exposure and control flammable gases/vapors. The vast majority of these systems are “sized” properly, meaning they move enough air to meet the code/standard they were built to; however, one aspect of the system we find is that over time, changes have been made that no bring into question the “design” of the system. In this article, I will take us on a ride through the International Mechanical Code (IMC) sections that define how our “make-up air” must be designed. I am using the IMC as that is the most common design used in the USA.
First, let’s look at Section 1105, which applies to Ammonia Engine/Machinery Rooms. Specifically, let’s look at 1105.6.2 Makeup Air…