Containment and Ventilation: Two Key Concepts for a Safe Application of SPF
By Stephen Wieroniey, Spray Foam Coalition
It is critical for applicators, helpers, and adjacent workers who may enter the spray foam application area before foam is fully cured, to follow good work practices in order to avoid potential exposure to spray polyurethane foam (SPF) component chemicals. Potential health effects from exposure above recommended levels or the occupation exposure limits (or “OEL”) can range from no effects to slight irritation of the eyes, skin or respiratory system to the development of chronic lung or pulmonary disease depending on the individual person, as well as the level and duration of overexposure.
Containment and ventilation are intended to reduce the potential for exposure of applicators, helpers, and others who may be working in areas adjacent to SPF application and chemicals. Personal protective equipment (PPE) is used in coordination with these engineering controls. In addition, restricting unauthorized access to the SPF work zone can help minimize potential exposures. One should also evaluate the feasibility of having individuals not involved in the application process vacate the work zone or entire building depending on the jobsite. Persons should return to the relevant area only after it is safe to do so.
The Basics of Containment and Mechanical Ventilation Systems
Proper containment and ventilation contribute to a safe workplace during the installation of SPF. Containment creates a restricted work zone and helps limit overspray while the ventilation system helps remove SPF component chemicals from the work zone.
Application of SPF to walls, ceilings, attics, and basements within buildings of varying size and geometry creates some challenges for designing containment and ventilation configurations because every job site can be different. The delivery rate and position of the spray gun, as well as air flow, is expected to change throughout the job as the applicator moves around the space.
The Basics of Work Zone Containment:
Sheeting is installed to separate the work zone from the remainder of the building. This separation also helps provide negative pressure when ventilating the work zone. Polyethylene sheeting can be used to build a containment area during SPF applications.
Penetrations and openings to other parts of the building, including open areas between the ceiling joists above the interior walls, are temporarily blocked with faced fiberglass batts, plastic sheeting, cardboard, landscaping cloth, or other materials. These penetrations and openings are also taped to minimize air flow as shown in Figure 1. Finished surfaces, such as windows and immovable furnishings and appliances, are masked to prevent overspray.
It is important to deactivate the HVAC system and cover HVAC registers and grilles (see Figure 2) during installation and ventilation of the work zone. Use OSHA’s Lock-out/Tag-out (LOTO) procedures to de-energize and secure the HVAC system breakers or sub-panel and/or use a sign/tape over the switch, as shown in Figure 3. After conditions are safe, turn the HVAC system back on after work site ventilation is stopped and prior to re-occupancy.
Mechanical ventilation of the work zone during and after SPF installation helps to keep the SPF work zone under a slight negative pressure, which reduces the airborne chemical concentrations of SPF component chemicals. The supply air system pushes air into the containment zone, delivering a positive pressure inside. The exhaust air system pulls the air from the containment zone, creating a negative pressure. To help assure that a net negative pressure is created in the containment zone, the exhaust air is pulled from the containment zone at a higher volume than the supply air pushed into it. The ventilation system would normally be ran during the entire application of SPF and for an appropriate time afterwards.
After SPF is applied, continue to follow the manufacturer’s instructions regarding ventilation rate and duration of ventilation in the work zone. Some of the factors affecting the ventilation period include specific SPF formulations and cure times, ventilation rate, and ambient temperature and humidity inside the containment area. During this time, consider establishing access restrictions, as all workers entering the area, will need appropriate PPE. Refer to the manufacturer’s directions for other trade workers’ re-entry times.
Re-entry and re-occupancy time is dependent on a number of factors including SPF formulation, the amount of foam applied per volume of space, temperature, humidity, the degree of ventilation, and other variables.
A ventilation system consisting of both active exhaust and supply air systems can address these issues. Figure 4 shows an example of a two-fan system.
There are several key points to consider when designing this type of system:
Maintain a negative pressure in the containment zone.
Remember: To create a net negative pressure the air pulled from the containment zone must exceed the air pushed into the area.
Check placement and direction of fans.
Generate and maintain air flow across the containment source.
Avoid unwanted openings in the containment zone.
Exhaust contaminants to an outside location that creates no safety risk.
Use filtration on the inlet of the exhaust system.
In summary, work zone containment and mechanical ventilation are necessary to protect workers, helpers, and adjacent workers during the application of high-pressure SPF and for an appropriate time afterwards.
It is important to take into account the specific conditions and circumstances relevant to your own spray foam application area, and follow the manufacturers’ recommendations for containment, ventilation, re-entry, and re-occupancy.
Re-entry and re-occupancy are not the same!
Re-entry time is the time elapsed after installation of SPF in a building when it is deemed safe for applicators, helpers, and other trade workers to enter the building and resume operations without the need for personal protective equipment.
Re-occupancy is the time elapsed after installation of SPF insulation in a building when it is deemed safe for building occupants or residents to resume normal building operations and activities.
Refer to the manufacturer’s instructions for specific guidance on re-entry and re-occupancy times.
The Spray Foam Coalition of the American Chemistry Council’s Center for the Polyurethanes Industry has more detailed guidance on ventilation during the installation of SPF, via the link provided below. Additional resources are available at www.spraypolyurethane.org.•
Download pdf of guidance on ventilation during the installation of SPF