4 FM quick reads on air quality
1. Web Tool Calculates Real Time Air Quality Index
Did you know you can find out the air quality index for over 300 cities with just a few clicks? At the AIRNow Web site, you can search for air quality conditions by zip code or state, or you can set up instant email notifications for your area.
The service covers over 300 cities and is free to use. Each report ranks different air quality parameters along a spectrum: good, moderate, unsafe for sensitive groups, unhealthy, very unhealthy and hazardous. The parameters listed in each report are today's and tomorrow's air quality index and forecasted ozone status. It also provides current conditions, along with time observed, regarding the current air quality index and current particle and ozone levels. Data is updated hourly.
Other interesting tools the website provides are a current visibility camera, air quality map archives, and links to local and state air quality resources.
An AIRNow mobile app is also available.
The AIRNow website was developed by the U.S. EPA, NOAA, NPS, tribal, state, and local agencies.
2. Keep Humidity Just Right For Good Indoor Air
Today's tip focuses on how relative humidity, both too high and too low, can have a negative effect on indoor air quality. In general, the sweet spot for humidity is somewhere between 30 and 60 percent relative humidity.
Don't operate your building at low relative humidity. One of the most irksome contributors to poor IAQ, especially in wintertime, is low relative humidity. Lowering the temperature in the occupied spaces is one practical way to improve this situation.
When the relative humidity in commercial and institutional buildings is low, occupant's mucous membranes in the nose, mouth and throat dry out. The result is they become much more sensitive to the ubiquitous pollutants found in an indoor environment. More cases of colds, allergies, and even nosebleeds are not uncommon.
The solution to this problem is difficult. Installing a central humidification system into the building's air handling system is often impractical and cost prohibitive. Individual space humidifiers can help, but they have stringent maintenance requirements which, if not adhered to, can present IAQ problems of their own.
But don't go overboard and make the mistake of operating your building at high relative humidity either. High humidity provides conditions for microbial growth. If high relative humidity conditions are a problem at your facility, consider using dehumidification equipment. You can also consider the use of high limit humidifier controls to prevent condensation on the inside surfaces of the downstream duct. Lastly, consider using unlined ductwork with external insulation directly downstream of the humidifiers or cooling coils to help prevent microbial contamination.
You can refer to ASHRAE Standard 55, "Thermal Environmental Conditions for Human Occupancy" for more detail on acceptable ranges for humidity.
3. Manage Indoor Pollutants to Preserve Indoor Air Quality
Today's tip from Building Operating Management is to control sources of indoor pollutants to safeguard indoor air quality. Rather than making the HVAC system the first line of defense, try to control pollutant sources locally. Localizing large pollutant contributors in separate rooms is an effective method of controlling contamination. These rooms should be maintained under negative pressure in relation to surrounding rooms and exhausted directly to the outdoors. Large contributors include photocopier rooms or special process print rooms.
Contaminant sensing can be used as a means to ensure there is adequate ventilation. In areas of a building where occupancy or contaminant levels are variable, consider the use of carbon dioxide, volatile organic compound, carbon monoxide or other contaminant-sensing inputs. HVAC systems can use the information from the contaminant-sensing inputs to control the amount of outdoor air introduced into an area within a building. When contaminant level thresholds are exceeded and the system calls for increased ventilation, precautions should be made that the outdoor air being brought in isn't itself contaminated.
You might also consider a night purge cycle. HVAC systems can often be programmed to operate on a night "flush" cycle on 100 percent outside air to clear out any unwanted indoor pollutants on a daily basis. However, this strategy is not advisable when the outside air is especially warm, humid or contaminated.
A good filtration system will also play a key role in preserving indoor air quality, even with these other measures in place. When possible, design or retrofit HVAC systems to incorporate high-efficiency filters. Some filtrations strategies to consider include:
- Consider upgrading filtration with a 30 percent ASHRAE prefilter and a 90 percent ASHRAE final filter, but first make sure the system can handle the additional pressure drop.
- Consider using antimicrobial filters.
- Make sure the filter system is properly sealed to eliminate filter bypass.
- Inspect the air filter system regularly.
- Change filters at the proper intervals. To help with this, use reliable filter gauges.
4. Good HVAC Maintenance Practices Mean Good Indoor Air Quality
Even the most sophisticated HVAC system will fail to provide good indoor air quality if not properly maintained, which makes developing an HVAC maintenance plan crucial to assuring the proper operation of the building's HVAC system so it can provide an acceptable indoor environment. Facility managers interested in fostering good indoor air quality should make certain to have an HVAC preventive maintenance program that includes:
&mdash: Scheduled inspection, cleaning and service.
&mdash: Calibration of control system components.
&mdash: Replacement parts that at least meet design specifications.
&mdash: Proper procedure documentation.
To facilitate inspection and maintenance of the duct system, facility managers should consider installing access doors in the HVAC ducts. The access doors should be gasketed and provide a tight seal. In addition, facility managers may also want to install access doors in the HVAC equipment if access is insufficient for inspection or maintenance.
Another component of good maintenance practices to protect indoor air quality is to make sure you're using proper levels of biocide in water treatment systems. Cooling towers are prime sources of microorganism growth. They require continuous attention. Periodic testing is also advisable.
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