Air Changes Per Hour
Below is a list for average air-changes per hour (ACH) required to properly ventilate different building types. ACH is defined as 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
Moffitt has been using this table for decades. Our ventilation design team can give you a quick estimate for your building ventilation just using the numbers above. ACH is used in the 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
Moffitt Can Help You Find Your Air Changes Per Hour
Moffitt can help you find the Air Changes per Hour for our plant. We can do either an estimate using the info 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.