Accredited Environmental Technologies, Inc.         

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IAQ 101 (Definte the Problem)

ANSI/ASHRAE/OSHA Recommended Standards

It's too Cold or it's too Hot

It's too Dry or Humid

An ounce of Prevention is worth a Pound of Response

You should've been here Yesterday

Quotes of the Month


"Success is to be measured not so much by the position that one has reached in life as by the obstacles which he has overcome." Booker T. Washington

"Success comes in cans; failures comes in can'ts."

"Success is not the key to happiness. Happiness is the key to success. If you love what you are doing, you will be successful" Herman Cain

"Success is simple. Do what's right, the right way, at the right time".
Arnold Glasqow


IAQ 101: Temperature and Humidity

Define The Problem

     The first step in an Indoor Air Quality (IAQ) investigation is to define the problem by by talking with building occupants, management, and maintenance personally to answer the following questions.

  1. Why has the client requested the IAQ Investigation?
  2. What are the building occupant concerns, complaints or symptoms? Due they clear up after leaving work (How soon)?
  3. When did the symptoms start; Is there any pattern, frequence or specific areas reported?
  4. Do symptoms correlate to any changes in the buildings HVAC systems?
  5. Do symptoms correlate to renovations/remodeling or occupancy changes?
  6. What has been previously implemented to resolve the problem?


     Rarely in today's modern buildings do windows open. Temperature and humidity control is provided by the building's HVAC system and designed to provide a work environment that is not too hot, cold, dry or humid, and is which free from drafts and objectionable odors.

     The ANSI/ASHRAE 55-2004 Standard for Thermal Environmental Conditions for Human Occupancy is the benchmark used in design, commissioning and testing of buildings and other occupied spaces and their HVAC system. Environmental factors addressed by this standard include temperature, thermal radiation, humidity, and air speed; Personal factors include activity and clothing. This standard includes temperature and humidity conditions which 80% of building occupants believe acceptable (comfortable).

     OSHA presents temperature and relative humidity guidelines within the OSHA Technical Manual (OTM). Associated interpretive documents state; "As a general rule, office temperature and humidity are matters of human comfort. OSHA has no regulations specifically addressing temperature and humidity in an office setting."

     AET recommends the following rule of thumb for T/RH conditions for use by building management in evaluating their building environments. 

Temperature                 68-76oF (Winter)
                                  73-79oF (Summer)

Relative Humidity           30-50% (Winter)
                                  40-65% (Summer)

Complaint.....It's too Cold or too Hot

     Temperatures that are too cold or too hot ranked as #1 and #2 on a list of top office complaints according to a survey by the International Facility Managers Association. Excessively high or low temperatures in an office area can lead to symptoms in building occupants and reduce productivity. High temperatures have been associated with fatigue, irritability, headache and a decrease in performance and alertness. Likewise, if the office is too cold, persons may experience discomfort to their hands and feet, shivering, fatigue and a decrease in performance and alertness.

     Remember, uniformity of temperature is important to comfort. Don't rely on your thermostat setting.

Be alert for:

  1. Poor thermostat location: Proper placement is essential. Keep away from indoor heat sources such as copy machines, perimeter walls and sunlight.
    Recommendation: Thermostats should be located in covered locked boxes, only able to be adjusted by building maintenance staff.
  2. Thermostat Dead Band: The dead band is the temperature range where neither heating or cooling takes place and the ventilation fan is off; Wide dead bands can result in large temperature fluctuations and inadequate ventilation. Recommendation: Adjust the thermostat dead band or replace with a model that maintains fan operations and narrows the dead band.
  3. Radiant Heat Gain/Losses: Persons in perimeter offices with large window areas can be uncomfortable even though the thermostat setting and the measured air temperature are within the comfort range. Complaints and large temperature variations can shift during the day and season as the sun angle changes.
    Recommendation: Add insulation to exterior facing walls and use curtains to reduce heating from direct sunlight. Utilize separate thermostats for perimeter locations.
  4. Temperature Stratification: If the air from the HVAC system is not properly mixed, the temperature near the ceiling can be several degrees warmer than at floor level (i.e. warm air rises and heavier, cooler air sinks). Non-carpeted floors can also be a cold source. Occupant discomfort can be related to the temperature of the floor.
  5. Drafts: Drafts can also be caused from radiant sources and convective currents. In addition, look for the positioning of desks, tables, etc. directly below supply air vents (especially cubicle areas) or in close proximity to radiant heat sources.


Complaint... It's too Dry or Humid

     Humidity refers to the amount of moisture in the air. Relative humidity (RH) is the percentage of water vapor in the air at a specific temperature compared to the amount of water vapor it is capable of holding at that temperature. Humidity is a factor of thermal comfort. Rising RH reduces the bodies ability to lose heat through perspiration and evaporation (similar to raising the temperature) .

     High humidity conditions (primarily occurs in the summer months) can result in persons feeling wet and clammy. RH levels exceeding 50-60% can promote mold growth, increase dust mites, and musty odors that can exacerbate allergies and asthma. High humidity can especially be a problem in new construction where internal walls are mostly made from paper-faced wallboard instead of wood or plaster which are more mold-resistant. ASHRAE 62.1-2007 states "Occupied space RH shall be limited to 65% or less." Recommendation: Dehumidifiers, heat and ventilation are the best way to reduce humidity levels particularly in basements and crawl spaces. These units can be connected to an external drain to promote continued operation.

     Low humidity conditions (primarily occurs in winter months) can dry the eyes, nose and respirator passages and increase building occupants susceptibility to upper respiratory infections and colds. Low humidity levels can also cause skin irritations and can also make you feel cooler resulting in the desire to turn the thermostat up. Static electricity problems affecting the hair and synthetic fiber clothing are good indications of an office with low RH (about 40% RH). Studies indicate odors become more objectionable at 30% RH and below. Contact lens users also have discomfort in low RH. Recommendation: AET does not generally recommend the use of humidifiers to increase the moisture in the air. AET's experience indicates that personal/room humidifiers can cause IAQ problems. These units must be properly maintained according to manufacturer instructions to control mold/bacteria growth within the units. This routinely requires (1) cleaning of the water in the holding tank every day (2) thoroughly cleaning the entire humidifier every 3 days and (3) using distilled water in the tank instead of tap water. Tap water contains minerals which when dispersed in the water mist form a "white dust" on walls and furniture once dried.

An Ounce of Prevention is Worth a Pound of Response

     AET recommends building managers purchase a digital Temperature/RH meter in order for building maintenance to perform periodic inspections/testing of work spaces. Proper temperature and humidity levels in your home or office increase comfort, save money on utility bills and promote a healthy environment. An accurate Temperature/RH meter is available at a cost less than $100.00 and help you identify and solve problems before symptoms and health issues arise.

You should Have been Here Yesterday...
24 -72 hour Testing or Hobo Use

     This is a frequent statement from building occupants to IAQ investigators. To this end, T/RH conditions can/do change by the hour or day based on building operations and HVAC performance. Spot T/RH checks can provide false data and should be verified by 24-72 hour testing to evaluate multiple HVAC cycles and building use.

     AET recommends the use of Hobo Data Loggers to evaluate intermittent T/RH complaints. These compact, battery operated devices can measure, record, and document T/RH levels at multiple locations for months at a time. Each device can store about 43,000 measurements.

     Real life solutions and cost saving recommendations including prevention of future complaints is AET's objective in every IAQ investigation.

Make AET your first point of contact for your environmental consulting needs in 2010.

CALL US NOW AT (800-9696-AET)


Alan Sutherland has been a Certified Industrial Hygienist since 1978 with over 30 years of CIH-related environmental consulting experience. He has a Masters Degree in Environmental Science from Drexel University and is the founder/owner of Accredited Environmental Technologies, Inc. (In 1984). He is uniquely trained and licensed as an Environmental Professional in both the field and laboratory. He has been the founder of two AIHA Accredited Laboratories and a mentor to six (CIHs). Mr. Sutherland is also a Certified Hazardous Material Manager. He can be reached directly at 610-891-0114 or email a.sutherland@aetinc.biz.

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