What role does air change rate play in controlling workplace airborne contaminants?

Air change rate describes how often the air within a space is replaced over a given period, usually per hour. It’s a key factor in controlling airborne contaminants because it determines how quickly pollutants are diluted and removed from the environment.

In workplaces where contaminants are generated, such as dusts, fumes, or vapours, a higher air change rate generally means contaminants are cleared more quickly. This reduces the time workers are exposed and helps keep concentrations lower overall.

However, air change rate works best as part of a wider control strategy. It’s not always suitable to rely on general ventilation alone, especially where contaminants are released at a specific point. In those cases, local exhaust ventilation is usually more effective.

If air change rates are too low, contaminants can accumulate. If they’re unnecessarily high, energy use increases and comfort can suffer. The right balance depends on the task, the layout of the space, and how contaminants behave once released.