How many broad composite categories does ANSI/ASHRAE 52.2 average particles in?

The correct answer is that ANSI/ASHRAE 52.2 categorizes average particles into three broad composite categories. This standard is focused on evaluating the performance of air filter media, and it classifies particles based on their size. The three size categories include:

1. PM10: Particles with a diameter of 10 micrometers or less. These can include dust, pollen, and mold spores.

2. PM2.5: Particles with a diameter of 2.5 micrometers or less. These are often associated with combustion processes and are important for health impacts due to their ability to penetrate deep into the lungs.

3. PM1: Particles with a diameter of 1 micrometer or less. This category often includes fine particles generated by industrial activities and other sources.

By breaking down particles into these three categories, ANSI/ASHRAE 52.2 provides a comprehensive way of assessing filter efficiency for varying particle sizes. Understanding these categories is crucial for selecting the appropriate air filter for different applications and environmental conditions.