VOCs are Volatile Organic Compounds. These compounds vaporize easily and circulate in the air. Some common VOCs are gasoline, alcohol, and formaldehyde. Not all VOCs are dangerous, but some types can be toxic in high concentrations. As indoor environments are often poorly ventilated, it is especially important to keep VOC concentrations low. https://www.epa.gov/indoor-air-quality-iaq/volatile-organic-compounds-impact-indoor-air-quality]
PM stands for Particulate Matter. The number that follows the “PM” is the width in microns of the particle. For example, PM 2.5 includes particles 2.5 microns wide. For reference, a human hair is about 100 microns in diameter. Small particles, like the ones measured by the Halo, can irritate your lungs and even get into your circulatory system. Some studies have found a close link between exposure to these particles and heart and lung disease. They can also worsen chronic disease such as asthma, heart attack, bronchitis and other respiratory problems.