Air-conditioned indoor environment. Air conditioning device controls the humidity, ventilation, and temperature to maintain a cool atmosphere. Could provide health benefits for breathing and for reducing harmful particulate matter through the various processes like filtration, humidification, cooling, and disinfection. For people with asthma or allergy to mold, it is advised to regularly change AC filters and use electrostatic filters that trap allergens.
Air conditioning can also be held responsible for a few health problems. If it is not properly maintained, it can actually facilitate the spread of micro-organisms such as Legionella pneumophila.
Air conditioning units can also generate sounds to which when someone is exposed over a considerably long period of time can lead to the individual's hear loss. 

Cleaning conditions, building characteristics, products used in households, cultural habits, climate and outdoor environment can also influence air-conditioned indoor air quality. ​

Air pollutants are small and larger particles that can be drawn into the body, biological matter such as pollen, microbes or hair, and gas molecules that can be harmful to humans, animals and food crops.
Pollen can be as small as 10 micrometers (µm), tobacco smoke particles are about 0.01 µm, and smog (translucent cubes of smoke and fog primarily resulting from automobile combustion) as small as 0.001 µm. 
The Clean Air Act requires EPA to set National Ambient Air Quality Standards (NAAQS)  for six common air pollutants: particle pollution, photochemical oxidants and ground-level ozone, carbon monoxide, sulfur oxides, nitrogen oxides, and lead. ​Examples of other toxic air pollutants include benzene, found in gasoline; perchlorethlyene, emitted from some dry cleaning facilities; methylene chloride, used as a solvent and paint stripper by a number of industries; asbestos released form some building materials, plastic and textiles; refrigerants released from vehicle air conditioners; airborne formaldehyde from smoke, cosmetics and disinfectants.  

hydrocarbon present in coal tar and petroleum, cigarette smoke, used in chemical synthesis, motor fuels, solvents, detergents, pesticides, personal care items such as nail polish or hair color and many other substances. It has a sweet, aromatic, gasoline-like odor. Benzene is a carcinogen that causes leukemia as well as a number of other illnesses. Virtually the entire U.S. population is exposed to benzene, at least in small amounts -- at gas stations (it's in the gasoline), in diesel exhaust or from cigarette smoke, including second-hand smoke. Benzene is also a problem in a number of workplaces, including oil refineries, coal-coking operations at steel mills, chemical processing plants, rubber manufacturing plants and laboratories, where it is often used as a solvent for other chemicals. You can avoid one significant source of benzene by stepping away from the gas pump when refueling your car.

Benzene levels in breath increase after exposure to tobacco smoke, but there are additional sources of benzene in breath than ambient air. It is difficult to establish exact relationships with the number of cigarettes smoked, or with other benzene exposures such as diet. 

​a colorless pungent gas (smell ranges from resembling of pickles to cloying to sickening and suffocating) mainly used in the production of industrial resins, e.g., for particle board and coatings for walls, cabinets and other furniture, in the manufacture of pesticides and disinfectants. It is the simplest aldehyde with formula CH2O , made by oxidizing methanol, and is also known by its systematic name methanal. In view of its widespread use, toxicity, and volatility, formaldehyde is a significant consideration for human health. Most industrial emissions of formaldehyde -- 42% -- are from the lumber industry, which uses adhesives containing formaldehyde to make plywood. Formaldehyde has been linked to lung cancer, and may also cause leukemia and asthma attacks. Diesel emissions also contribute to formaldehyde pollution, and NRDC's ongoing work to clean up diesel is having an important impact.
To minimize formaldehyde exposures at home, make sure any wood furniture or fixtures that use particleboard are laminated or otherwise coated, choose exterior- rather than interior-grade pressed wood products for remodeling and be sure that areas where you are using products containing formaldehyde are well ventilated.

Formaldehyde can be detected in human breath and, like "breathalyzer" test, is a reliable indicator of formaldehyde levels in blood. It can be also detected in urine. In an older study (Berthold Moser, et al., Respiratory Physiology & Neurobiology, Vol. 145, Issues 2-3, February 2005), the median level of formaldehyde in human breath was 4.3 parts per billion (ppb) with levels of 6.3 ppb, 40 ppb and 73 ppb of the 75th, 97.5th and maximum percentiles, respectively. 

solid or liquid particles found in the air with a diameter of 10 micrometers or less (0.0004 inches or one-seventh the width of a human hair). EPA's health-based national air quality standard for PM-10 is 50 µg/m3 (measured as an annual mean) and 150 µg/m3 (measured as a daily concentration). Particulate matter 2.5 micrometers or less in diameter. (PM2.5) is generally described as fine particles
PM10 and PM2.5 particles make up a large proportion of dust that can be drawn deep into the lungs. Some particles are large or dark enough to be seen as soot or smoke. Others are so small they can be detected only with an electron microscope. Larger particles tend to be trapped in the nose, mouth or throat.
Because particles originate from a variety of mobile and stationary sources (diesel trucks, cars, woodstoves, power plants, lawn mowers, leaf blowers, volcanoes, etc.), their chemical and physical compositions vary widely. 

male fertilizing agent of flowering plants, trees, grasses and weeds. A major allergen that causes symptoms of seasonal allergic rhinitis (hay fever).

Because pollen are small, light and dry, they can be easily spread by wind, which keeps pollen airborne and carries it over long distances. When the air is humid, such as during or after it rains, pollen becomes damp and heavy with moisture, keeping it still and on the ground.
Allergy symptoms are often minimal on days that are rainy, cloudy or windless, because pollen does not move about during these conditions. Hot, dry and windy weather signals greater pollen and mold distribution and therefore, increased allergy symptoms.
Pollen from plants with bright flowers, such as roses, usually do not trigger allergies. These large, waxy pollen are carried from plant to plant by bees and other insects. On the other hand, many trees, grasses and low-growing weeds have small, light, dry pollen that are well-suited for dissemination by wind currents. These are the pollen that trigger allergy symptoms.


fine to coarse powdery substance comprising pollen grains which are male microgametophytes of seed plants, which produce male gametes (sperm cells).
plants that are known to cause pollen allergies:

• Trees:  Birch, Alder, Cedar, Hazelnut, Willow, Plane, Olive and Hornbeam
• Grasses:  Ryegrass & Timothy
• Weeds:  Ragweed, Nettle, Mugwort, Goosefoot & Sorrel

colorless gas with a fishlike odor at low concentrations changing to ammonia-like odor at higher concentrations. Trimethylamine (TMA) exposure can lead to transient increase in resistance to antibiotic stress associated with medium alkalinization, and could also contribute to the evolution of antibiotic tolerance in bacterial populations. Long-term inhalation of low concentrations or short-term inhalation of high concentrations has adverse health effects.
People with fish-odor syndrome (trimethylaminuria) have an impaired version of the enzyme flavin-containing monooxygenase 3 (FMO3). This is the enzyme that converts trimethylamine to non-odorous trimethylamine N-oxide. Trimethylamine in breath can be also used in diagnostics of renal and liver diseases, and for real-time monitoring of haemodialysis efficiency. 

One of the most important dietary sources of trimethylamine is choline found in most protein foods, especially eggs, liver, kidney, peas, beans, peanuts, soya products and cruciferous vegetables (brussels sprouts, broccoli, cabbage and cauliflower).

Spegazzinia mold is a genus of mitosporic Ascomycota (sac fungi that accounts for approximately 75% of all described fungi). There are seven species of this mold including Spegazzinia deightonii, Spegazzinia tessarthra, Spegazzinia sp. CL115, Spegazzinia sp. yone 279 and other species. Spegazzinia grows in slightly warm to tropical temperatures in soil, trees and plants and may be also found in air but does not grow on indoor environmental surfaces. Personal spore traps may be a better measure of exposure than stationary air sampling equipment.