Final answer:
The question addresses the requirements for mechanical ventilation in a dwelling unit when air infiltration is below a certain threshold. Mechanical ventilation compensates for low air exchange rates to ensure a healthy indoor environment by providing necessary oxygen and reducing the concentration of pollutants.
Step-by-step explanation:
The question pertains to the standards for air infiltration and mechanical ventilation in a dwelling unit. When the air infiltration rate of a dwelling unit is tested to be less than the specified standard, additional mechanical ventilation is necessary.
Mechanical ventilation is essential in maintaining a healthy indoor environment by supplying oxygen for breathing and diluting pollutants. While measures like weather stripping, caulking, and improved window seals help to reduce unwanted air infiltration, they can lead to very low air exchange rates if not balanced with appropriate ventilation systems, increasing pollutant levels inside the dwelling.
It is crucial that dwellings maintain an adequate air exchange rate to ensure both energy efficiency and indoor air quality. Without this balancing act, air turnover times could exceed healthful levels, necessitating the inclusion of mechanical ventilation solutions.