Air Changes Per Hour
The below table indicates the range of average air-changes per hour (ACH) required to properly ventilate each building type. ACH is the number of times the air within a defined space is replaced each hour. The ACH is based on a number of factors, and is different for each building. However over the decades that we’ve been designing ventilation systems, we’ve come to use these ranges and averages to help make some quick calculations.
Read on to find the ranges, and average ACH for more than 30 common building types.
Building Air Changes per Hour Chart
| Building Type | ACH Ranges | Average ACH |
| Beater Room | 30 | 30 |
| Boiler Room | 30 – 60 | 45 |
| Bottle Pasteurizing | 20 – 30 | 25 |
| Box Annealing | 20 | 20 |
| Breweries Fermenting Room | 20 – 30 | 25 |
| Compressor | 15 – 20 | 17.5 |
| Dye Houses | 10 – 15 | 12.5 |
| Electric Furnace | 60 – 120 | 90 |
| Engine Room | 30 | 30 |
| Forge Shop | 35 | 35 |
| Foundry – Core Rooms | 40 – 60 | 50 |
| Foundry – Cupola Building | 30 – 40 | 35 |
| Foundry – Moulding Section | 20 – 30 | 25 |
| Foundry – Pouring Section | 20 – 30 | 25 |
| Galvanizing Room | 15 – 20 | 17.5 |
| Gas Producer Building | 10 -20 | 15 |
| Generating Room | 20 | 20 |
| Glass Furnaces | 60 – 120 | 90 |
| Glass Plant | 30 – 60 | 45 |
| Heat Treating Room | 60 – 120 | 90 |
| Keg Washing & Storage | 8 – 12 | 10 |
| Machine Shop | 10 – 15 | 12.5 |
| Oil Refineries – Pump House | 15 – 20 | 17.5 |
| Packing, Meat – Slaughter House | 5 -10 | 7.5 |
| Packing, Meat – Smoke House | 30 | 30 |
| Paint Spray Area | 60 – 90 | 75 |
| Paper Mill | 20 | 20 |
| Pickling – Continuous | 10 – 15 | 12.5 |
| Pickling, Open Type | 40 | 40 |
| Steel Furnace Building | 45 | 45 |
| Sugar Mill – Main Building | 15 – 20 | 17.5 |
| Sugar Mill, Battery and Press | 15 | 15 |
| Textile Mill | 10 – 15 | 12.5 |
| Transformer Room | 30 | 30 |
| Turbine Room, Electricity | 15 | 15 |
| Warehouse | 4 – 5 | 4.5 |
| Zinc Smelting Building | 60 | 60 |
Finding Air Changes Per Hour
In the event that you need a more exacht ACH assessment for your building, our team uses the following equation; ACH=60Q/Vol, where:
- ACH = number of air changes per hour
- Q = flow rate of air in cfm
- Vol = volume L × W × H, in cubic feet
Our ventilation design team utilizes the equation above to find the exact ACH required for your building. While our table is certainly effective, finding the exact ACH will be neccesary for finding the perfect ventilation solution.
Moffitt Can Find Your Air Changes Per Hour
Moffitt can help you find the Air Changes per Hour required for your plant. We can do either an estimate using the info from the table above or a more accurate reading with a site visit by one of our District Solutions Providers. Fill out the form today to find your building’s ACH.