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Course 750 - Introduction to Industrial Hygiene

Safety guides and audits to make your job as a safety professional easier

Indoor/Outdoor Air Quality



Air contaminants are commonly classified as either particulate or gas and vapor contaminants. The most common particulate contaminants include dusts, fumes, mists, aerosols, and fibers.

Gases are formless fluids that expand to occupy the space or enclosure in which they are confined. Examples are welding gases such as acetylene, nitrogen, helium, and argon; and carbon monoxide generated from the operation of internal combustion engines or by its use as a reducing gas in a heat treating operation. Another example is hydrogen sulfide which is formed wherever there is decomposition of materials containing sulfur under reducing conditions.


Fumes are formed when material from a volatilized solid condenses in cool air. In most cases, the solid particles resulting from the condensation react with air to form an oxide.

Liquids change into vapors and mix with the surrounding atmosphere through evaporation.

Mists are finely divided liquid suspended in the atmosphere. They are generated by liquids condensing from a vapor back to a liquid or by breaking up a liquid into a dispersed state such as by splashing, foaming or atomizing. Aerosols are also a form of a mist characterized by highly respirable, minute liquid particles.


Vapors are the gaseous form of substances that are normally in a solid or liquid state at room temperature and pressure Vapors are formed by evaporation from a liquid or solid and can be found where a worker would clean and/or paint as well as where solvents are used.

Dusts are solid particles that are formed or generated from solid organic or inorganic materials by reducing their size through mechanical processes such as crushing, grinding, drilling, abrading or blasting.

Fibers are solid particles whose length is several times greater than their diameter.

1. Solid particles whose length is several times greater than their diameter are called _____.

a. fibers
b. fumes
c. vapors
d. dusts

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Indoor Air Quality

Dr. Julie Riggs - Indoor Air Quality.

Definition: Indoor air quality refers to the presence or absence of air pollutants in buildings. There are many sources of indoor air pollutants. The presence of sources of indoor air pollutants such as tobacco smoke and radon, or by conditions that promote poor indoor air quality such as inadequate ventilation or moisture intrusion that can lead to mold growth, are used as indications of potential health effects.

The quality of indoor air inside offices, schools, and other workplaces is important not only for workers' comfort but also for their health. Poor indoor air quality (IAQ) has been tied to symptoms like headaches, fatigue, trouble concentrating, and irritation of the eyes, nose, throat and lungs. Also, some specific diseases have been linked to specific air contaminants or indoor environments, like asthma with damp indoor environments. In addition, some exposures, such as asbestos and radon, do not cause immediate symptoms but can lead to cancer after many years.

Many factors affect IAQ. These factors include poor ventilation (lack of outside air), problems controlling temperature, high or low humidity, recent remodeling, and other activities in or near a building that can affect the fresh air coming into the building. Sometimes, specific contaminants like dust from construction or renovation, mold, cleaning supplies, pesticides, or other airborne chemicals (including small amounts of chemicals released as a gas over time) may cause poor IAQ.

The right ventilation and building care can prevent and fix IAQ problems.

2. Indoor air quality refers to _____.

a. the presence or absence of air pollutants in buildings
b. the presence or absence of humidity found within buildings
c. the presence or absence of ventilation within a building
d. the presence or absence of mold within a building

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Indoor Air Quality (Continued)

In approximately 500 indoor air quality investigations in the last decade, the National Institute for Occupational Safety and Health (NIOSH) found that the primary sources of indoor air quality problems are:
  • Inadequate ventilation 52%
  • Contamination from inside building 16%
  • Contamination from outside building 10%
  • Microbial contamination 5%
  • Contamination from building fabric 4%
  • Unknown sources 13%

Recommended Ventilation Rates

The 62-1989 standard recommends a minimum of 15 CFM of outdoor air per person for offices (reception areas) and 20 CFM per person for general office space with a moderate amount of smoking. Sixty cubic feet per minute per person is recommended for smoking lounges with local mechanical exhaust ventilation and no air recirculation.

Acute Health Effects of Major Indoor Air Contaminants


Employee complaints can be due to two types of building problems: sick or tight building syndrome and building related illnesses.

Sick building syndrome is a condition associated with complaints of discomfort including headache; nausea; dizziness; dermatitis; eye, nose, throat, and respiratory irritation; coughing; difficulty concentrating; sensitivity to odors; muscle pain; and fatigue. The specific causes of the symptoms are often not known but sometimes are attributed to the effects of a combination of substances or individual susceptibility to low concentrations of contaminants. The symptoms are associated with periods of occupancy and often disappear after the worker leaves the worksite.

Building-related illnesses are those for which there is a clinically defined illness of known etiology and include infections such as legionellosis and allergic reactions such as hypersensitivity diseases and are often documented by physical signs and laboratory findings. A more thorough description of these illnesses can be found in the American Conference of Governmental Industrial Hygienists (ACGIH) guidelines on evaluating bioaerosols.

3. Which of the following is a condition associated with complaints of discomfort that often disappear after leaving work?

a. Workplace flu
b. Building-related stress
c. Sick building syndrome
d. Legionellosis

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Indoor Air Quality (Continued)

Although asbestos and radon have been listed below, acute health effects are not associated with these contaminants. These have been included due to recent concerns about their health effects. The investigator should be aware that there may be other health effects in addition to those listed.

Acetic Acid

Sources: X-ray development equipment, silicone caulking compounds.

Acute health effects: Eye, respiratory and mucous membrane irritation.


Carbon Dioxide

Sources: Unvented gas and kerosene appliances, improperly vented devices, processes or operations which produce combustion products, human respiration.

Acute health effects: Difficulty concentrating, drowsiness, increased respiration rate.

Carbon Monoxide

Sources: Tobacco smoke, fossil-fuel engine exhausts, improperly vented fossil-fuel appliances.

Acute health effects: Dizziness, headache, nausea, cyanosis, cardiovascular effects, and death.


Sources: Off-gassing from urea formaldehyde foam insulation, plywood, particle board, and paneling; carpeting and fabric; glues and adhesives; and combustion products including tobacco smoke.

Acute health effects: Hypersensitive or allergic reactions; skin rashes; eye, respiratory and mucous membrane irritation; odor annoyance.

Nitrogen Oxides

Sources: Combustion products from gas furnaces and appliances; tobacco smoke, welding, and gas- and diesel-engine exhausts.

Acute health effects: Eye, respiratory and mucous membrane irritation.


Sources: Copy machines, electrostatic air cleaners, electrical arcing, smog.

Acute health effects: Eye, respiratory tract, mucous membrane irritation; aggravation of chronic respiratory diseases.


Sources: Ground beneath buildings, building materials, and groundwater.

Acute health effects: No acute health effects are known but chronic exposure may lead to increased risk of lung cancer from alpha radiation.

Volatile Organic Compounds (VOCs)

Volatile organic compounds include trichloroethylene, benzene, toluene, methyl ethyl ketone, alcohols, methacrylates, acrolein, polycyclic aromatic hydrocarbons, and pesticides.

Sources: Paints, cleaning compounds, moth-balls, glues, photocopiers, "spirit" duplicators, signature machines, silicone caulking materials, insecticides, herbicides, combustion products, asphalt, gasoline vapors, tobacco smoke, dried out floor drains, cosmetics and other personal products.

Acute health effects: Nausea; dizziness; eye, respiratory tract, and mucous membrane irritation; headache; fatigue.

4. Acute health effects of Carbon Monoxide are _____.

a. difficulty concentrating, drowsiness, increased respiration rate
b. eye, respiratory, and mucous membrane irritation
c. nausea, dizziness, and fatigue
d. dizziness, headache, nausea, cyanosis, cardiovascular effects, and death

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Indoor Air Quality (Continued)

Miscellaneous Inorganic Gases

Includes ammonia, hydrogen sulfide, sulfur dioxide.

Sources: Microfilm equipment, window cleaners, acid drain cleaners, combustion products, tobacco smoke, blue-print equipment.

Acute health effects: Eye, respiratory tract, mucous membrane irritation; aggravation of chronic respiratory diseases.


Sources: Insulation and other building materials such as floor tiles, dry wall compounds, reinforced plaster.

Acute health effects: Asbestos is normally not a source of acute health effects. However, during renovation or maintenance operations, asbestos may be dislodged and become airborne. Evaluation of employee exposure to asbestos will normally be covered under the OSHA Asbestos standard.

Synthetic Fibers

Sources: Fibrous glass and mineral wool.

Acute health effects: Irritation to the eyes, skin and lungs; dermatitis.


Tobacco Smoke

Sources: Cigars, cigarettes, pipe tobacco.

Acute health effects: Tobacco smoke can irritate the respiratory system and, in allergic or asthmatic persons, often results in eye and nasal irritation, coughing, wheezing, sneezing, headache, and related sinus problems. People who wear contact lenses often complain of burning, itching, and tearing eyes when exposed to cigarette smoke. Tobacco smoke is a major contributor to indoor air quality problems. Tobacco smoke contains several hundred toxic substances including carbon monoxide, nitrogen dioxide, hydrogen sulfide, formaldehyde, ammonia, benzene, benzo(a)pyrene, tars, and nicotine. Most indoor air particulates are due to tobacco smoke and are in the respirable range.

Microorganisms and Other Biological Contaminants (Microbials)

Includes viruses, fungi, mold, bacteria, nematodes, amoeba, pollen, dander, and mites.

Sources: Air handling system condensate, cooling towers, water damaged materials, high humidity indoor areas, damp organic material and porous wet surfaces, humidifiers, hot water systems, outdoor excavations, plants, animal excreta, animals and insects, food and food products.

Acute health effects: Allergic reactions such as hypersensitivity diseases (hypersensitivity pneumonitis, humidifier fever, allergic rhinitis, etc.) and infections such as legionellosis are seen. Symptoms include chills, fever, muscle ache, chest tightness, headache, cough, sore throat, diarrhea, and nausea.

5. Miscellaneous inorganic gases include _____.

a. viruses, fungi, mold, bacteria, nematodes, amoeba, and pollen
b. fibrous glass and mineral wool
c. ammonia, hydrogen sulfide, sulfur dioxide
d. trichloroethylene, benzene, and toluene

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Outdoor Air Quality

Air Quality 101 - DEQ Louisiana

The Clean Air Act requires the Environmental Protection Agency (EPA) to set National Ambient Air Quality Standards for six common air pollutants. These commonly found air pollutants (also known as "criteria pollutants") are found all over the United States. They are particle pollution (often referred to as particulate matter), ground-level ozone, carbon monoxide, sulfur oxides, nitrogen oxides, and lead. These pollutants can harm your health and the environment, and cause property damage. Of the six pollutants, particle pollution and ground-level ozone are the most widespread health threats. EPA calls these pollutants "criteria" air pollutants because it regulates them by developing human health-based and/or environmentally-based criteria (science-based guidelines) for setting permissible levels. The set of limits based on human health is called primary standards. Another set of limits intended to prevent environmental and property damage is called secondary standards.

Six Common Outdoor Air Pollutants


In the earth's lower atmosphere, ground-level ozone is considered "bad." Motor vehicle exhaust and industrial emissions, gasoline vapors, and chemical solvents as well as natural sources emit NOx and VOC that help form ozone. Ground-level ozone is the primary constituent of smog. Sunlight and hot weather cause ground-level ozone to form in harmful concentrations in the air. As a result, it is known as a summertime air pollutant. Many urban areas tend to have high levels of "bad" ozone, but even rural areas are also subject to increased ozone levels because wind carries ozone and pollutants that form it hundreds of miles away from their original sources.

"Good" ozone occurs naturally in the stratosphere approximately 10 to 30 miles above the earth's surface and forms a layer that protects life on earth from the sun's harmful rays.

Particulate Matter


"Particulate matter," also known as particle pollution or PM, is a complex mixture of extremely small particles and liquid droplets. Particle pollution is made up of a number of components, including acids (such as nitrates and sulfates), organic chemicals, metals, and soil or dust particles.

The size of particles is directly linked to their potential for causing health problems. EPA is concerned about particles that are 10 micrometers in diameter or smaller because those are the particles that generally pass through the throat and nose and enter the lungs. Once inhaled, these particles can affect the heart and lungs and cause serious health effects. EPA groups particle pollution into two categories:

  • "Inhalable coarse particles," such as those found near roadways and dusty industries, are larger than 2.5 micrometers and smaller than 10 micrometers in diameter.
  • "Fine particles," such as those found in smoke and haze, are 2.5 micrometers in diameter and smaller. These particles can be directly emitted from sources such as forest fires, or they can form when gases emitted from power plants, industries and automobiles react in the air.

6. Of the six common air pollutants, which are the most widespread health threats.

a. sulfur oxides and lead
b. particle pollution and ground-level ozone
c. carbon monoxide nitrogen oxides
d. hydrogen sulfide and oxygen

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Outdoor Air Quality (Continued)

Carbon Monoxide

Carbon monoxide (CO) is a colorless, odorless gas emitted from combustion processes. Nationally and, particularly in urban areas, the majority of CO emissions to ambient air come from mobile sources. CO can cause harmful health effects by reducing oxygen delivery to the body's organs (like the heart and brain) and tissues. At extremely high levels, CO can cause death.

Nitrogen Oxides

Nitrogen dioxide (NO2) is one of a group of highly reactive gasses known as "oxides of nitrogen," or "nitrogen oxides (NOx)." Other nitrogen oxides include nitrous acid and nitric acid. While EPA's National Ambient Air Quality Standard covers this entire group of NOx, NO2 is the component of greatest interest and the indicator for the larger group of nitrogen oxides. NO2 forms quickly from emissions from cars, trucks and buses, power plants, and off-road equipment. In addition to contributing to the formation of ground-level ozone, and fine particle pollution, NO2 is linked with a number of adverse effects on the respiratory system.

Sulfur Dioxide

Sulfur dioxide (SO2) is one of a group of highly reactive gases known as "oxides of sulfur." The largest sources of SO2 emissions are from fossil fuel combustion at power plants (73%) and other industrial facilities (20%). Smaller sources of SO2 emissions include industrial processes such as extracting metal from ore, and the burning of high sulfur containing fuels by locomotives, large ships, and non-road equipment. SO2 is linked with a number of adverse effects on the respiratory system.


Lead (Pb) is a metal found naturally in the environment as well as in manufactured products. The major sources of lead emissions have historically been from fuels in on-road motor vehicles (such as cars and trucks) and industrial sources. As a result of EPA's regulatory efforts to remove lead from on-road motor vehicle gasoline, emissions of lead from the transportation sector dramatically declined by 95 percent between 1980 and 1999, and levels of lead in the air decreased by 94 percent between 1980 and 1999. Today, the highest levels of lead in air are usually found near lead smelters. The major sources of lead emissions to the air today are ore and metals processing and piston-engine aircraft operating on leaded aviation gasoline.

7. Which of the following common air pollutants can cause harmful health effects by reducing oxygen delivery to the body's organs and tissues?

a. carbon monoxide
b. nitrogen oxides
c. sulfur dioxide
d. ozone

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