IAQ Tools for Schools
IAQ Reference Guide
Appendix J - Portable Classrooms
Recent surges in student population fueled an explosion in the use of portable classrooms in many parts of the country. Health-related concerns associated with portable classrooms have arisen. Teachers in the new units frequently complain of chemical odors. In older units, odor problems are often associated with moldy classroom carpets. Both new and older units are often subject to complaints about poor ventilation and indoor air quality (IAQ).
- Indoor Air Quality and Portable Classrooms
- Recommendations for Schools Using Portables
- Additional Resources
Indoor Air Quality and Portable Classrooms
All school buildings use similar construction and furnishing materials, so the types of chemicals present in the indoor air are not likely to be different for portable versus permanent classrooms. However, pressed-wood products, which may contain higher concentrations of formaldehyde, are used more frequently in factory-built portable units than in buildings constructed on-site. As a result, concentrations of some airborne chemicals may be higher in new portable classrooms, especially if ventilation is reduced.
The most common problems with portable classrooms include:
- Poorly functioning ventilation systems that provide inadequate quantities of outside air;
- Poor acoustics due to loud heating and cooling systems;
- Chemical off-gassing from pressed wood and other high-emission materials, which may be of greater concern because of rapid occupancy and poor ventilation after construction;
- Water entry and mold growth; and
- Site pollution from nearby parking lots or loading areas.
Recommendations for Schools Using Portables
Although portable classrooms are often the lowest cost option for housing students, they range in quality. Care should be taken during specification and selection to ensure that the health of the students is not compromised on inexpensive, low quality designs. When districts specify a portable design, they typically create a term contract that other districts can use to purchase the same (or slightly different) design. This practice (often called "piggy-backing") can save a district valuable time and money on specifications and approvals, but it can also compound poor decisions made by the original procurement.
Like all school facilities, portable classrooms should contain appropriate building materials and properly designed ventilation systems to minimize the presence of indoor air pollutants. Commissioning and regular maintenance are also important to maintain the quality of the indoor environment.
The following steps can help schools maintain a healthy indoor environment in their portable classrooms:
Specifying New Portable Classrooms
- Specify the appropriate vapor barrier location for exterior wall construction, consistent with the climate where the classroom will be used.
- When specifying a new portable classroom, ensure that the heating, ventilation, and air-conditioning (HVAC) system can:
- provide a minimum of 450 cfm of OUTSIDE air (based on 30 occupants at 15 cfm/occupant); and
- heat and cool this outdoor air at design outdoor air temperatures for the specific geographic location where each classroom is installed.
- Order an additional "outdoor air kit" since manufacturers do not include outdoor air intakes in their standard classroom models. Outdoor air intakes should not be located under portable units; these areas are typically not well ventilated and are prone to moisture, biological contaminants, and other pollutants.
- Outdoor air should be supplied continuously when a classroom is occupied. In order to provide a continuous outdoor air supply, it is important to ensure that the HVAC thermostat fan switch is set in the "on" or continuous mode when occupied.
- Air filters are needed for protection of HVAC components and reduction of airborne dust, pollens, and micro-organisms from recirculated and outdoor air streams. Air filters should have a spot rating between 35 and 80 percent or a Minimum Efficiency Rating Value (MERV) of between 8 and 13.
- If carpets are specified, use carpets that have been tested under the Carpet and Rug Institute’s Green Label Carpet Testing Program. Do not use carpet in entryways to classrooms with direct outdoor access. Supply waterproof mats and walk-off mats over carpeted entryways and other areas used for drying clothing and umbrellas.
- Locate classroom away from areas where vehicles idle or water accumulates after rains.
- Ensure that at least one supply air register and return air grille are located in each enclosed area. Also, make sure that building air intakes are located away from any exhaust outlet(s) or other contaminant sources.
- Specify operable windows to provide user-controlled ventilation when needed.
- Locate HVAC and air handler units as far away as possible from teaching areas to reduce noise.
- Specify minimal use of VOC emitting building materials.
- Install an awning over the portable’s entrance to help prevent rain and snow from blowing directly into classrooms.
- Specify complete documentation of operation and maintenance requirements.
- Prior to occupancy of any new portable units, operate HVAC systems at their maximum outdoor air intake rate continuously for several days. Start the "flush out" as soon as the HVAC system is operational, and continue after furniture installation. During this period, do not re-circulate return air. In humid climates, avoid introducing significant amounts of moisture during the flush out.
- Measure the amount of outdoor air entering the outdoor air intake of the HVAC unit to ensure it meets or exceeds the amount specified or 15 cfm per person, whichever is greater.
- Do not "bake out" the unit. "Bake out" is defined as increasing temperatures up to 100oF in order to "artificially age" building materials. Its effectiveness has not been proven and it may in fact damage parts of the HVAC system or building components.
- Establish and implement an Integrated Pest Management plan.
Operations and Maintenance
- Provide training on operation and maintenance of new HVAC equipment for appropriate staff. Instruct teachers and staff on proper use and settings of thermostat and ventilation controls.
- Train teachers how to minimize potential toxic emissions from the decorations and cleaning materials used in their classrooms. Develop and implement a "list of things to do before starting the class," including ensuring that the ventilation system is operating at least one hour before the class starts and watching for rust spots, wet spots, and other signs of deterioration of infrastructure. Teachers should also be educated about the potential risks of turning off HVAC systems.
- Establish a regular and timely plan for testing, inspecting, and performing specific maintenance tasks: Inspect roofs, ceilings, walls, floor, and carpet for evidence of water leakage (e.g., stains), and for mold growth or odor. Replace water-damaged materials promptly and fix leaks as soon as possible.
- For more information about portable classrooms and recommendations for designing, constructing, and renovating school facilities to maintain good IAQ see EPA’s IAQ Design Tools for Schools at www.epa.gov/iaq/schooldesign
- National Clearinghouse for Educational Facilities Portable Classrooms/Modular Construction Resource List available at www.edfacilities.org/rl/portable.cfm
- California Advisory on Relocatable and Renovated Classrooms available at www.ewg.org/files/advisory.pdf