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Health and Indoor Air Quality

Indoor Air Quality - IAQ, UV And People's Health

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Health and Indoor Air Quality
 

According to the Environmental Protection Agency (EPA), 10% of all colds are caught outdoors, 90% are caught indoors! We’ve all watched helplessly as a cold virus passed from one member of the family to another.

Perhaps you suffer from asthma or allergies and despite desperate attempts to dust more, keep the windows closed, clean your bedding, clothing, carpeting and furniture more frequently, your symptoms still persist.

The EPA states that indoor air can be up to 70 times more polluted than the outdoor environment. One reason for this is that the HVAC duct work is full of airborne germs, their particles and by products. These microbes are alive and thriving inside the furnace or air conditioning systems. The airborne germs adversely affect the air quality as they are blown past the furnace or air conditioning filter and circulated throughout the buildings. In some cases allergy or asthma symptoms can be triggered by the airborne microorganisms that are spread by the HVAC system.

In-duct and upper air UV air cleaners can be used to disinfect the indoor air and kill or inactivate the pathogenic microorganisms. A specialized application of germicidal UV on the coiling coil can also help by eliminating microbial growth from the coil and drain pan.

UV Health Facts

Why is UV-B harmful while UV-C (germicidal UV) is not? - The difference has to do with the ability of UV rays to penetrate body surfaces. UVC has an extremely low penetrating ability. It is nearly completely absorbed by the outer, dead layer of the skin (stratum corneum) where it does little harm. It does reach the most superficial layer of the eye where overexposure can cause irritation, but it does not penetrate to the top of the lens of the eye and can not cause cataracts. UVC is completely stopped by the ordinary eye glasses and by ordinary clothing.

How much UV exposure is considered safe? The National Institute for Occupational Safety and Health (NIOSH) has established safe exposure levels for each type of UV. These safe exposure limits are set below the levels found to cause eye irritation, eye being the body part most sensitive to UV. For germicidal UV (253.7nm) the irradiance limit is set to 0.2W/cm. See sidebar for UV exposure details →

How can people be certain they are not overexposed to UV? When upper room UV is first installed it must be checked with a sensitive UV meter to make sure reflected UV is less than 0.2W/cm at eye level. UV air cleaners must be installed well above eye level - usually 7 feet above the floor. UV tubes (lamps) within the air cleaners should not be directly visible from within 30 feet. Safety is assured if UV measurements at eye level meet NIOSH standards.

What are the symptoms and signs of UV overexposure? UV overexposure  causes an eye inflammatory condition known as photokeratitis. For 6 to 12 hours after an accidental overexposure the individual may feel nothing unusual, followed by the abrupt sensation of foreign body or "sand" in the eyes, redness of the skin around the eyes, some light sensitivity, tearing, and eye pain. The acute symptoms last 6 to 24 hours and resolve completely without long-term effects. Overexposure of the skin resembles sunburn but does not result in tanning.

What precautions are needed with overhead germicidal UV? Fixtures must be turned OFF when cleaning, inspecting or changing the lamps. Persons hypersensitive to sunlight may need to wear protective glasses, clothing or use sunscreen on exposed skin. No special protection is needed for most people.

UV light Next UV Topic - Indoor Air Pollution

 

Ultraviolet Light
"Germicidal ultraviolet light installed in HVAC systems has gained great popularity over the last several years. Unfortunately, many of the claims by over-zealous manufacturers and distributors are exaggerated
and some just blatantly false. While there is no one cure for indoor air quality problems, ultraviolet light technology does provide benefits and can be part of an overall Indoor Air Quality improvement plan."
Indoor Air Quality Association
Uv light fights allergy, asthma, mold
 
UV Exposure Level
The American Conference of Governmental Industrial Hygienists (ACGIH) Committee on Physical Agents has established a TLV (Threshold Limit Value) for UV-C exposure to avoid skin and eye injuries. For 254nm UV, this TLV is 6mJ/cm over an eight-hour period.

The TLV function differs by wavelengths because of variable energy and potential for cell damage. This TLV is supported by the International Commission on Non-Ionizing Radiation Protection and is used in setting lamp safety standards by the Illuminating Engineering Society of North America. This TLV is interpreted as if eye exposure in rooms is continuous over eight hours and at the highest eye-level irradiance found in the room. In those highly unlikely conditions, a 6mJ/cm dose is reached under the ACGIH TLV after just eight hours of continuous exposure to irradiance of 0.2 W/cm. Thus, 0.2W/cm is widely interpreted as the upper permissible limit of irradiance at eye height.

Safety of Upper-Room Ultraviolet Germicidal Air Disinfection for Room Occupants

Health and Indoor Air Quality
 

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