Seven Special IAQ Challenges
- By Michael Fickes
- February 1st, 2007
The variety of facilities on college and university campuses ensures that facility managers will not only deal with basic indoor air quality (IAQ) questions, but also tougher, more intractable IAQ challenges that affect kitchens, print shops, labs, and other distinctive spaces. Here’s a look at seven special campus IAQ challenges and suggested solutions.
Kitchens — Kitchens must exhaust a lot of air to remove humidity and cooking odors.To maintain a balanced pressure, you have to introduce an equal amount of make-up air, said Gary Luepke, systems engineer with Trane in LaCrosse, WI.Make-up air has to be heated or cooled and perhaps dehumidified, and that can be costly.
Without sufficient make-up air — which is defined as the amount or percentage of fresh air delivered or mixed with recirculating air on a normal cycle of air by volume — the kitchen will draw air from surrounding spaces, such as the dining hall or the outside, continued Luepke. Air will find other routes — through cracks in exterior brick walls, for example. In winter, cold air sucked into the walls could freeze pipes. During the summer, humid, moist air in the walls can condense on cold pipes and cause corrosion or mold.
Worse, inadequate make-up air could cause equipment to malfunction. It can cause a chimney to suck air in from the outside when it is supposed to go the other way, said William A. Turner, MS, PE, a principal with Harrison, ME-based Turner Building Science & Design, LLC, a firm that specializes in designing healthy indoor environments. It can blow out pilot lights and back-draft through gas appliances. Usually you need one machine to suck air out and one to push air in. You should run them both.
Print Shops — Photo reprographics areas and print shops should follow the same ASHRAE guidelines, said Turner. The guidelines call for print shops to move air outside through a separate, dedicated exhaust system. If you are running a laser printer in the shop, you are mixing iron filings, carbon black, and styrene and melting it onto paper, he said. This produces fugitive emissions that will stay in the space if you don’t exhaust the air in the room. Again, when you exhaust, you need make up air. ASHRAE recommends doing this by transferring air from an adjoining space into the space where it will be exhausted.
Chemistry Labs — Chemistry labs have issues similar to kitchens, said Luepke. Students work under hoods that contain gasses and exhaust them out of the building. Again, you need make-up air, he continued. While kitchens receive make-up air equal in volume to exhausted air, a lab calls for slightly less make-up air. This sets the air pressure in the room at a lower or negative level compared to the pressure in adjacent spaces. If the hood doesn’t capture all the fumes, the negative pressure prevents them from getting out of the room. Instead, air always flows into the room and up into the hood where it is exhausted.
It’s expensive to cool or heat make-up air, noted Luepke. For that reason, some labs are installing variable air volume hoods, in which the amount of air exhausted can be tailored to specific needs. Students set the variable air volume control on the hood as they work.
Chemistry lab hoods exhaust air, but biology labs often use bio-safety hoods that recirculate air through a HEPA (high efficiency particulate air) filter, said Turner. ASHRAE covers science lab IAQ standards in great detail, he added.
Libraries, Media Centers, and Paper File Warehouses — The goal here is to control humidity and prevent the build up of dirt, Turner said. Mold is a concern in a warehouse, he continued. And media centers need specific humidity and temperature conditions to preserve books.
Museums — Some museums and other facilities sensitive to moisture in the air may require heating, ventilating, and air-conditioning (HVAC) systems modified to control humidity, too. With a direct humidity control system, you set the temperature — and you set a limit for the relative humidity, Luepke said. When the humidity rises above the setting, the HVAC system cools and dehumidifies the space. Since there has been no call for temperature control, the space can become too cold, and you may have to reheat the air to maintain the temperature. The heat can come from the HVAC system, an energy transfer device, or both.
Athletic Facilities — Athletic facilities are usually exhausted, said Turner. The biggest difference between athletic facilities and other spaces that exhaust air is part-load operation. If a few people are in the gym, you want to run the system at a lower level than if there is a game.
Some athletic facilities have special needs. Swimming pools, for instance, require an air temperature several degrees warmer than the water in the pool. That keeps the moisture in the pool and out of the air, Turner said.
All Basements — Turner’s pet IAQ concerns include basements. The cold temperature of the earth makes it easy for a concrete foundation 12 ft. below the surface to reach the dew point, condense moisture out of the air, and grow mold. The only way around this is a good commercial dehumidifier, Turner said. He recommends models rated at 100 pints for 10 amps, set to self-drain to a sink or sump.
After IAQ Comes IEQ — Luepke cautions against thinking you’re done once you have solved your special IAQ problems. Then comes IEQ, or ‘indoor environmental quality,’ he says. That brings in issues such as natural light compared to artificial light, the quality of acoustics, and other indoor environmental features.
Location of Outdoor Air Intakes and Exhaust
The following actions, recommended by the U.S. Environmental Protection Agency, detail what to consider when locating the outdoor air intakes and exhaust portions of a traditional ventilation system to provide an appropriate quantity and quality of outdoor air, lower energy costs, and easier maintenance.
Proper location of outdoor air intakes can minimize the blockage of airflow and intake of contaminated air. The bottom of air intakes should be at least eight in. above horizontal surfaces (generally the ground or the roof) to prevent blockage from leaves or snow. In northern locations, more separation may be needed due to greater snow depths or drifting snow.
Intakes should not be placed within 25 ft. of any potential sources of air contaminants, including sewer vents, exhaust air from the facility, loading docks, vehicle loading areas, garbage receptacles, boiler or generator exhausts, and mist from cooling towers. If the source is large or contains strong contaminants, or if there is a dominant wind direction in the area, the minimum separation distance may need to be increased. Air admittance valves, an inexpensive and code-approved one-way air valve, can be added to sewer vents to eliminate the potential for release of gases into the surrounding air.
Grilles protecting air intakes should be bird- and rodent-proofed to prevent perching, roosting, and nesting. Waste from birds and other pests (e.g., rats) can disrupt proper operation of the HVAC system, promote microbial growth, and cause human disease. The use of outdoor air intake grilles with vertical louvers, as opposed to horizontal louvers, will reduce the potential for roosting.
Intake screens must be accessible for inspection and cleaning. In existing facilities, an insufficient amount of ventilation air is often the result of clogged intake screens that are inaccessible for inspection and cleaning. Screens hidden by an intake grille should be designed with a grille that is easily opened, such as a hinged grille with two quick-release latches, or in the worst case, a grille with four one-quarter-turn fasteners. All screens should be easily removable for cleaning.
Consider adding a section of sloped intake plenum that causes moisture to flow to the outside or to a drain if intake grilles are not designed to completely eliminate the intake of rain or snow.
Source: U.S. Environmental Protection Agency (www.epa.gov).