Calculating ventilation requirements means determining how much fresh air you must supply and exhaust to control heat, contaminants and air quality. In industrial plants and mines, this is a critical design step that is governed by regulations, engineering standards and safety considerations.
The first step is to define the purpose of ventilation in the space. Common objectives include providing enough oxygen for people, diluting gases and fumes, controlling dust concentrations, removing heat from equipment and maintaining comfortable temperatures. Each objective may lead to a different minimum airflow requirement, and the final design typically uses the highest of these values.
For general building and light industrial ventilation, designers often use air changes per hour (ACH) or airflow per person. ACH is calculated by multiplying the room volume by the desired air changes and dividing by 60 to obtain a flow rate in m3/min or CFM. For example, if a workshop has a volume of 3000 m3 and the recommended rate is 6 ACH, the required airflow is 3000 × 6 / 60 = 300 m3/min, or 18,000 m3/h. Standards and guidelines provide typical ACH values for different types of spaces.
In industrial and mining applications, ventilation requirements are often based on more specific criteria. In underground mines, regulations may specify minimum airflow per worker, per kilowatt of diesel equipment or per tonne of production, as well as maximum allowable concentrations of gases such as CO, NOx and methane. Engineers calculate the total diesel power, expected emission rates and heat loads, then size main and auxiliary fans so that airflow is sufficient to dilute contaminants below legal limits and remove heat from the workings.
For processes that generate fumes, dust or vapours, such as welding, grinding or chemical mixing, local exhaust ventilation may be required in addition to general ventilation. In these cases, formulas for hood capture velocity, duct transport velocity and enclosure leakage are used to calculate the airflow needed at each source. The total system requirement is then the sum of all local exhaust flows plus the general supply air needed to replace them.
After establishing the required volume flow, engineers check whether the proposed ventilation layout will provide adequate air distribution. It is not enough to supply the right total airflow; the air must reach all critical locations, such as underground headings, machine areas and occupied zones. Computational models, empirical rules and field measurements help verify that velocities and directions are acceptable.
In summary, you calculate ventilation requirements by combining occupancy, heat and contaminant criteria with regulatory standards, using tools such as air changes per hour, airflow per person, airflow per kW and source specific capture formulas. For industrial plants and mines, this calculation is the foundation for selecting the right fans and designing a safe, effective ventilation system.
