Figure: 25 TAC §297.8(b)(4)

TABLE 1. Common Indoor Air Conditions/Contaminants in Government Buildings

Condition Or Contaminant

Major Sources

Comfort/Health Effects

MRL Guidelines (1)



Weather, occupants, equipment, and HVAC systems.

Normally a comfort and productivity issue; high temperature may cause heat stress.

72 to 76 degrees Fahrenheit in the summer and 70 to 75 degrees Fahrenheit in the winter. Control within range of ± 2 degrees Fahrenheit for a given day.

Comfort related to temperature, relative humidity (RH), air velocity, and occupant preferences, activity and attire.

Relative Humidity (RH)

Moisture produced from weather, occupants, and other water sources.

Normally a comfort and productivity issue; high RH may cause "sticky feeling", and moisture damage to building contents; low RH may cause dry/itchy eyes, mucous membranes and skin.

30-60 %
30-50 % preferred for better mold prevention.
For low RH regions: <30% acceptable if no occupant discomfort.

Comfort related to temperature, RH, air velocity, activity and attire. Below 50% prevents most mold growth.

Air Velocity

HVAC systems, individual and equipment fans, significant area pressure changes.

Being too hot or too cold within the recommended temperature and relative humidity ranges, dry eyes, sore throats and nasal irritation.

25 to 55 feet per min (fpm).

Comfort related to temperature, RH, air velocity, activity and attire.

(allergy is a hypersensitivity to a substance that does not normally cause a reaction)

Allergies may be caused by protein or an antigen. Animal dander, cockroach droppings, dust mite fecal matter, insects and insect parts, dust, latex.

Sneezing, runny or congested nose, coughing, wheezing, postnasal drip, sore throat, watering eyes, itching eyes, nose and throat, and allergic shiners (dark circles under the eyes).

Cat: 8 µg/g

Dust Mite: 2 µg/g

Cockroach: 5 µg/g

According to National Institute of Health as many as 50 million Americans are affected by allergic diseases.

(fibrous material)

Building materials such as ceiling textures, wall compounds, resilient floor covering, pipe insulation.

Lung cancer, asbestosis, dyspnea, interstitial fibrosis, restricted pulmonary function and eye irritation.

0.01 fibers per cubic centimeter (f/cc)

Asbestos containing materials should not be used or installed in building.

Carbon Dioxide
(Odorless gas)

Occupants’ respiration; unvented or poorly vented indoor combustion sources; vehicle exhaust via traffic and parking garages; and outside air.

Indicator of amount of outside air in area. High levels may result in complaints of odors, "stuffy air", sleepiness, fatigue, and headaches.

700 ppm above outdoor level - should trigger concern over adequate fresh air.

Acceptable levels should prevent complaints of odors (body odors) and stuffy air.

Carbon Monoxide
(Odorless gas)

Outside air, unvented or poorly vented indoor combustion sources, such as gas heaters and appliances; and vehicle exhaust in parking garages.

Headaches, dizziness, and nausea. At moderate concentrations, angina, impaired vision and reduced brain function. High levels can be fatal.

9 ppm for 8 hrs.

35 ppm for 1 hr

If the inside CO level exceeds the outside CO level, look for a possible inside source.

If high levels of CO suspected, remove occupants.
Blood analysis can verify exposure if done within an hour.

Environmental Tobacco Smoke

Tobacco combustion.

Group A carcinogen by EPA, respiratory effects, multiple effects on children.

No level is considered acceptable, particularly for children and non-smokers.

Surgeon General recommends smoking only be allowed inside buildings if smoking area has separate ventilation system.

Formaldehyde (HCHO)
(pungent odor)

Pressed-wood products (e.g. furniture and furnishings), embalming fluid, textiles and foam insulation.

Irritant of eyes, and respiratory tract, sensitizer, and possible carcinogen.

0.04 ppm

Odor Threshold: 0.05-1.0 ppm

Tobacco smoke and other combustion sources are secondary sources.

Fungi (mold, mildew, yeasts)

Outdoor air-not normally a major source in building with good air filtration systems.

Wet/damp building materials and furnishings, particularly after 24 hours. Air handling systems. Poorly maintained indoor plants. Spoiling food.

Allergies (most common) - Sneezing, runny or congested nose, coughing, wheezing, and postnasal drip, sore throat, watering eyes, and itching eyes, nose and throat.
Difficulty breathing. Nose, throat, skin and eye irritation, rashes, headaches, and less common symptoms (i.e., aches, fever, fatigue, and central nervous system problems).

Visible mold on surfaces or mold odors is unacceptable.

Dry or discard water-damaged materials within 24 hours.

Maintain relative humidity <60%(preferably <50%) year round.

Rely on visual inspection, odors, history of moisture problems and occupant complaints and health symptoms.
Remove mold growth and eliminate source of moisture.

Hydrogen Sulfide (H2S)
(rotten egg odor)

Sewer gas
Dry drain traps or broken sewer lines.

Irritant to eyes and respiratory tract, headache, dizziness, and nausea.

0.07 ppm

Odor 0.001 ppm

Water must be kept in p-traps of drains that are connected to sewer lines.

Lead (Pb)
(dust or fumes containing lead)

Paint, dust, welding and soldering activities and outdoor air

Brain damage, particularly in children under 6 years old, weakness, and anemia.

0.0015 mg/m3

Flaking lead-based paint a concern. Certain lead-based paint abatement activities are regulated.


Natural and man-made stagnant water sources. Warm conditions and certain pH conditions will accelerate growth.

Legionnaires’ disease: form of pneumonia. Mild cough and low fever to rapidly progressive pneumonia and coma. Early symptoms include malaise, muscle pain, and headache; later symptoms include high fever, dry cough and shortness of breath.

Prevent sources of stagnant water, particularly warm sources that rapidly produce bacteria; or if not preventable, periodically chemically or thermally disinfect.

For hot water sources: holding temperature:
140 oF; delivery temperature: 122 oF, or monthly thermally disinfect.

Mercury (Hg)
(Silver-white, heavy liquid metal)

Thermometers, barometers, batteries, fluorescent light bulbs, blood pressure devices and electrical switches.

Irritation to eyes, skin, cough, chest pain, trouble breathing depending on exposure.

0.0002 mg/m3


Nitrogen Dioxide
(acrid odor)

Leaking vented combustion appliances, unvented combustion appliances, outdoor air, diesel engines near loading docks. Welding, tobacco smoke.

Irritation to eyes, nose, throat.
May induce cough. At higher concentrations depending on exposure time may result in chronic bronchitis, chest pain and pulmonary edema.

0.05 ppm


Ozone (O3)
(pungent odor)

Electrostatic appliances, office machines, ozone generators, outdoor air.

Irritation to eyes and mucous membranes. Pulmonary edema and exposure times may lead to respiratory disease.

0.05 ppm

Can damage plants, some materials, particularly rubber-containing materials and certain plastics.

Particulate Matter (dust)
(non-toxic particles; toxic particles covered elsewhere)

Construction and renovation activities, movement of materials, paper dust from printers, dust-producing activities and numerous outside sources.

Sneezing, coughing and itchy eyes. Some particles more hazardous than others, and can cause irritation to eyes and lungs. Respirable particles of greater hazard concern.

PM10 - 150 µg/m3 (24 Hour)*
PM 2.5 - 65 µg/m3 (24 Hour) and 15 µg/m3
(Annual Mean)*

* See 40 CFR 50.7 for definitions and additional information.

(includes insecticides, fungicides, rodenticides, termiticide, herbicides, and fumigants.

Direct indoor application of pesticides by occupant or commercial applicator. Outside, particularly near agriculture and fogging for mosquitoes or other pests.

Irritation of eyes and mucous membranes, headache, dizziness, weakness, tingling sensation, nausea, blurred vision, vomiting, tremors, abdominal cramps, chest tightness, and liver damage.
Some are possible carcinogen(s).
Avoid skin contact with pesticides.
Organochlorine and organophosphorus pesticides are generally more toxic than other type pesticides.

2,4-D 0.01 mg/m3
2,4,5-T 0.10 mg/m3
DDT 0.001 mg/m3
Aldrin 0.0025 mg/m3
Benomyl 0.05 mg/m3
Chlordane 0.005 mg/m3
Chlorpyrifos (Dursban) 0.002 mg/m3
Dichlorvos 0.009 mg/m3
Diazinon 0.001 mg/m3
Heptachlor 0.0005 mg/m3
Malathion 0.05 mg/m3
Paraquat 0.001 mg/m3
Parathion 0.0005 mg/m3
Pyrethrum 0.05 mg/m3
Roundup 0.05 mg/m3
Sevin 0.050 mg/m3
Warfarin 0.001 mg/m3

Avoid use of chemical pesticide treatments if possible. Chlordane, heptachlor, aldrin, and dieldrin should not be used. Chlorpyrifos (Dursban) and Diazinon should not be used indoors.

Recommend use of businesses that conform to 22 Texas Administrative Code, §595.14 Reduced Impact Pest Control Services.

Radon (Rn)
(naturally occurring, odorless, radioactive gas)

Soil, rocks, and water from the natural breakdown (radioactive decay) of uranium. Radon also breaks down into radioactive decay products.

Radon and its decay products emit ionizing radiation which if inhaled can damage the lung tissue and may cause lung cancer over time.

4 picocuries per liter of air (pCi/L)

Buildings can inexpensively be tested for radon

Sulfur Dioxide (SO2)
(pungent odor)

Unvented space heaters (kerosene), other combustion sources, outdoor air.

Eye irritation, skin irritation, respiratory irritation

0.01 ppm


Volatile Organic Compounds (VOCs)
(many are odorless, some have odor)

New building materials and furnishings, consumer products, maintenance materials, outdoor air, cleaners, personal care products, tobacco smoke, paints, pesticides, solvents, combustion processes.

May cause variable responses such as irritation of eyes, nose and upper respiratory tract, headaches, lightheadedness, and nausea. A few VOCs have been directly linked to cancer in humans and others are suspected of causing cancer.

Acetone 26 ppm
Alkanes C4-C16 (if not listed) 2.5 mg/m3
Alkanes >C16 0.07 mg/m3
Aromatic distillates, light 0.17 ppm
Aromatic distillates, heavy 0.43 ppm
Benzene 0.05 ppm
2-butoxyethanol 6 ppm
decane 1.22 ppm
Ethylbenzene 1.0 ppm*
Gasoline (<0.9% benzene) 0.83 ppm
n-hexane 0.6 ppm
isobutane 3.4 ppm
isopropyl alcohol 2.2 ppm
Methylene chloride 0.6 ppm
Naphtha, coal tar 0.62 ppm
Naphthalene 0.002 ppm**
Styrene 0.06 ppm**
Tetrachloroethylene 0.2 ppm
1,1,1-trichloroethane 1.4 ppm
Trichloroethlyene 0.175 ppm
Toluene 1 ppm
Xylenes (o,m,p) 1 ppm

For total VOCs:
0.3-3 mg/m3 - complaints possible;
>3 mg/m3 -complaints likely.

Product emission rate should not result in an indoor concentration level greater than 0.5 mg/m3 of total VOCs.
* level for 14 to 364 days exposure
** level for 365 days and longer exposure


(1) MRL = Minimum Risk Level

      Concentration units not defined in table:

mg/m3 = milligrams of contaminant per cubic meter of air
ppm = parts of contaminant per million parts of air (on a volume per volume basis)
µg/g = micrograms of contaminant per gram of material