4 FM quick reads on indoor air quality
1. 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.
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.
Maintaining IAQ During Construction Projects
When undertaking renovations or other major construction projects at a facility, maintaining indoor air quality should be on the list of project to-dos. Even when using the lowest VOC emitting products available, there will probably still be some dust, fumes or vapors to contend with.
Isolate occupants and the HVAC system that serves them from the construction zone. Isolate the construction zone from the occupied areas with physical barriers, such as plastic sheeting, that inhibit air movement.
Exhaust air from the construction zone directly to the outside such that it is maintained at a negative pressure with respect to other areas. If the HVAC system serving the construction zone serves other areas, completely seal potential return air paths to prevent construction dust, fumes and vapors from being recirculated to other zones.
As well, evaluate the need to upgrade the filtration system during construction projects. Don't underestimate the importance of frequent air filter inspections and changes both in the new and old systems during and shortly after the construction process.
Also, consider the use of gas-phase filtration to eliminate chemicals that may be generated during the construction project.
Indoor Air Quality Measurement Strategies
When it comes to measuring for good indoor air quality and the strategies to employ in pursuing remediation, it really pays to first stop and consider what you really want to achieve.
Consider this from Andrew Persily, leader of the Indoor Air Quality Group at the National Institute of Standards and Technology: "You can spend a lot of money measuring different things, but what are you going to do with the information?" he says. "There are potentially hundreds of different contaminants that could be measured but there aren't established criteria for what's acceptable in non-industrial settings. So unless there's a really good reason for measuring the contaminant and you know what you're going to do with the data, many would recommend against it."
So if it's something obvious, such as you smell mold or you see it, you're probably better off spending your money cleaning it up and addressing the problem that's causing it so you don't get mold again. If all you do is test it without addressing the cause, all you're doing is spending money.
If it's something more subtle than obvious mold, or it's not something clear-cut like cold air blowing on people, it is improper to call a specialist who has only one sphere of expertise. Don't hire a specialist before consulting a generalist.
If workers have symptoms, contact the expert who understands symptoms, how to connect them to the indoor environment, and whom to contact for specific remediation needs.
And even when you have the expert involved, don't permit tests to be performed unless the consultant can explain the results.
Have the expert explain what information the testing will provide and how that information will be used. Again, it's become relatively easy to test for substances. It's not so easy to connect the findings of those tests to human health effects.