Particulate Contaminants

Particulate matter is the name for a wide range of airborne particles that are small enough for people to breathe in. Particulate matter found in indoor air can cause respiratory symptoms such as coughing and wheezing.

There are two categories of indoor air pollutants that can affect the quality of air in a home: particulate matter and gaseous pollutants.

Particulate matter (PM) is composed of microscopic solids, liquid droplets, or a mixture of solids and liquid droplets suspended in air. Also known as particle pollution, PM is made up of a number of components, including acids such as nitric and sulfuric acids, organic chemicals, metals, soil or dust particles, and biological contaminants. Among the particles that can be found in a home are:

• Dust as solid PM or fumes and smoke, which are mixtures of solid and liquid particles.
• Biological contaminants, including viruses, bacteria, pollen, molds, dust mite and cockroach body parts and droppings, and animal dander.

Particles come in a variety of sizes. Small particles can be fine or coarse. From a health standpoint, fine particles that have a diameter of 2.5 micrometers (µm) or less are the largest concern. These particles can penetrate deep into the lungs where they may cause acute or chronic health effects. Coarse particles, between 2.5 and 10 µm in diameter, usually do not penetrate as far into the lungs and tend to settle in the upper respiratory tract. Large particles, greater than 10 µm in diameter, or roughly one-sixth the width of a human hair. They can be trapped in the nose and throat and expelled by coughing, sneezing, or swallowing.

Mechanical Ventilation Systems
Heating, Ventilation and Air Conditioning (HVAC) systems perform these important tasks:

• They bring fresh air indoors;
• They vent stale air outside;
• They circulate the air throughout the building; and
• They control temperature and humidity levels.

Mechanical filters can be installed on your furnace or as part of the ventilation system. There are also stand-alone devices designed to capture particles from the air in room-sized areas. Filters must be replaced according to the manufacturer's instructions in order to be effective.

• Electronic air cleaners use an electrical field to trap particles. They can be a part of the ventilation system or a stand-alone device, and some even produce ozone as a by-product.

• Ion generators use static charges to trap particles and are only available as portable units. Some ion generators also produce ozone as a by-product.

• Hybrid models are air cleaners that incorporate two or more of the air cleaner types mentioned above into a single product and are becoming more and more common.