Clothes dryer exhaust systems that exceed what CFM must be equipped with make up air?

In the context of clothes dryer exhaust systems, there is a specific requirement for make-up air, which is essential for ensuring safe and efficient operation. When a dryer exhaust system exceeds 200 CFM (Cubic Feet per Minute), it is necessary to provide make-up air to replace the air being exhausted. This is crucial because the high rate of exhaust can create negative pressure in the home or commercial space, leading to issues such as backdrafting or insufficient air for combustion appliances, which can pose safety risks.

Make-up air helps maintain balanced air pressure in the environment, preventing hazardous conditions that can arise from a lack of sufficient air supply. By requiring make-up air for exhaust systems that exceed this threshold, building codes and safety regulations ensure that homes and commercial buildings remain safe and well-ventilated while using high-capacity dryer systems. Thus, the requirement for make-up air at this specified CFM threshold is an important aspect of ventilation and airflow management in HVAC systems.