Particulate Matter (PM) is a mixture of solid and liquid particles that are suspended in the air. These are categorized into coarse, fine and ultrafine. PM2.5 are fine particles that have a diameter less than 2.5 micrometers (more than 100 times thinner than a human hair) and remain suspended in the air for longer durations. … Continue reading What Is PM2.5 and How Does It Affect Indoor Air?