Small and tiny particles that float in the atmosphere for a while and do not immediately fall. These particles are divided into groups according to size. Particulate matter is harmful to health. This is true as much for increased concentrations over a short period of time as for low level exposure over a longer period. For this reason, we should aim to minimize exposure to particulate pollution at all times.

An organic chemical that is very prevalent in our environment. It is a colorless gas compound with a pungent odor from a family of gases called aldehydes. It is a sensitizing agent that can cause an immune system response upon initial exposure. It is also a suspected human carcinogen that is linked to nasal cancer and lung cancer. Formaldehyde exposure is most common through gas-phase inhalation. Airborne concentrations of formaldehyde above 0.1 ppm can cause irritation of the respiratory tract.

Organic chemicals that have a high vapor pressure at ordinary room temperature. Some VOCs are dangerous to human health or cause harm to the environment. Anthropogenic VOCs are regulated by law, especially indoors, where concentrations are the highest. Harmful VOCs typically are not acutely toxic but do have compounding long-term health effects. Because concentrations are usually low and symptoms slow to develop, research into VOCs and their effects is difficult.

Odors are the human body’s olfactory perception a particular chemical or chemical mixtures. These odorous chemicals come from mold, bacteria, sewer gases, decomposing rodents or their waste, combustion gas fumes (car or furnace), and pets (to name a few of the common sources). These certainly affect indoor environmental quality problems in buildings. Some chemicals (at low concentrations) can be health hazards even before they are detected by the nose, while others are irritating at relatively high concentrations but not a health hazard for most people (people with environmental or chemical sensitivities may have health effects at very low concentrations of many chemicals). Although most chemical contaminants originate from within the building, chemicals can be drawn into a building from the outdoors as well.

Molds and other allergens. Around 30% of the world’s population suffers from allergies. Approximately 86% of all allergy sufferers are allergic to pollen. During times of high pollen concentrations, allergies can manifest themselves in the form of colds, swollen nasal membranes, sneezing attacks and watery eyes, adversely affecting the lives of sufferers.