What is the formula to calculate outdoor air supply in terms of concentration?

The formula for calculating outdoor air supply in terms of concentration involves understanding the relationship between the concentrations of contaminants in different air zones. Specifically, the formula utilizes the concentrations of the contaminated air (Cr), the outdoor air (Co), and the supply air (Cs).

In this context, the correct formula, which is represented by the answer provided, directly relates to determining how much outdoor air contributes to achieving a specific desired concentration within an enclosed space.

The formulation accounts for the following aspects:

• Cr denotes the concentration of contaminants in the return air.

• Co represents the concentration of contaminants in the outdoor air, which is often lower or can be perceived as fresh air.

• Cs indicates the concentration in the supply air that can be mixed with return air to dilute the contaminants.

By rearranging and taking into account these relationships, the calculation effectively assesses the contribution of outdoor air to the indoor air quality, illustrating how the proportions of different air streams affect the overall concentration of contaminants. This is crucial for industrial hygiene assessments aimed at ensuring healthy environment standards.

Utilizing this correct formula also implies that a significant understanding of air dilution principles is at play in maintaining air quality, which is essential for industrial hygienists.