Air temperature is one of the most important factors in home comfort, just because the human body likes to function within a familiar range of temperatures, generally between 23 and 26 degrees Celsius (68 and 79 Fahrenheit). But that's not all there is to it. Higher air temperatures may accelerate mold and bacteria growth.
Temperatures outside the comfort zones affect the feeling of dissatisfaction with the indoor air quality (IAQ) and the number of people who experience sick building syndrome.
The American Society of Heating, Refrigerating, and Air-Conditioning Engineers (ASHRAE) established a standard for air comfort in 2001. The standards specify characteristics of ventilation and air conditioning systems as well as basic acceptable air temperature standards.
The Nature of Air Contamination
The standards recognize several sources of contamination that affect IAC.
- Microbial contamination, mold and mildew particles.
- Chemical contamination in the form of particles and chemicals.
Contamination may come from inside
- People themselves.
- Generated by indoor activities.
- Operating machinery.
- Volatile organic compounds (VOCs) that outgas from manufactured construction materials and cleaning products.
Or contaminants can be brought in from outside.
- They may enter through fresh air ventilation.
- Open doors or windows.
- pollen, dust, fungal spores,
- industrial pollutants,
- vehicle exhaust,
- odors from dumpsters,
- odors that were vented out, but which come back in or come from other buildings.
- Soil gases like radon,
- fuel tank leakage,
- pesticides or odors from landfills.
The complex of potential contaminants makes removal complex. The best practice is to remove the contaminants close to their sources using local exhaust systems. But local exhaust is not always possible.
There are four fundamental elements of indoor air quality, four methods of controlling contaminants.
- Source control--eliminating the contaminant itself or neutralizing it.
- Ventilation--removing the contaminant by moving it from the environment.
- Humidity management--water particles hold contaminants in a breathable form.
- Filtration--using effective filters to contain contaminants for later removal.
Temperature Effects That Eventually Reach Indoor Air [EPA Report to Congress]
Temperature stratification when air that is warmer rises and cooler air falls. More or less stable layers of air can trap heavier contaminants in the lower layers and lighter contaminants in higher layers where they remain more or less stable.
If air is not properly mixed, the natural pattern caused by convection will create more or less stable air levels so of which may hold intensified concentrations of pollutants.
Even if air is properly mixed, uninsulated areas on the floor over unheated spaces can create discomfort zones in local areas. Large fluctuations of indoor temperature can occur where there is control "dead band," a temperature range within which neither heating or cooling takes place.
Where some heating comes from radiant heat, the bands of energy may be narrow so that some people may experience excess heat and others, cold, below the average temperature of the room.
Humidity is a factor in thermal comfort as well. When relative humidity on the room goes up, more moisture is held in the air and the ability of the air to evaporate perspiration goes down as does the feeling of being cooled by perspiration evaporation.
Relative humidity can have the same effect on comfort as raising the temperature. Both excessive relative humidity, causing a feeling of stuffiness and overheated conditions, and very dry air, causing too much cooling, can produce discomfort.
Inversion is a factor. Some scientists believe that cool air is cleaner than warm air. The chemical reactions that create ozone are increased at higher temperatures, especially under sunlight. Ozone has an irritating effect on respiration.
Trees absorb fewer pollutants in warm air than cold air, according to a study from the Stockholm Environment Institute. However, when cold and warm layers of air are inverted and a mass of warm air is trapped under a cold air envelope, pollutants absorbed in the warm air stabilize at a level where people are most exposed to it.
Dust Goblin has been manufacturing Air Filters in the U.S.A. for over 60 years. Please contact us to find out more.