Safety Report

Steps contractors can take to ensure indoor air quality

Part two

In part one, which was published in the Winter 2017 issue, we covered planning and hazard assessment. In this column, we cover testing and monitoring, engineering and work-practice controls, and reporting and responding.

Testing and monitoring

Once all the potential hazard sources are identified, a plan of routine monitoring and testing should be developed. This testing is usually accomplished by a highly trained, skilled and qualified person, such as a certified industrial hygienist (CIH), a chemical engineer or a certified hazardous materials manager (CHMM), but some testing and monitoring can be done by site safety staff.

Depending on the hazards identified, testing and monitoring may include:

  • Inspecting all interior areas for mold and moisture and ensuring that proper measures are being employed to protect absorbent materials — such as drywall, insulation materials, ceiling tiles and wood structures — from exposure to moisture.
  • Duct inspections of the HVAC system to confirm they are clean and dry.
  • Thermal imaging photography supplemented by surface moisture meter readings to ensure the properties are dry and free of invisible moisture.
  • Screening for airborne mold.
  • Surface qualitative and quantitative testing for mold.
  • Surface or airborne dust characterization.
  • Combustion by-product screening and oxygen level testing.
  • Testing for indoor air quality-related volatile organic compounds (TVOC).

Testing and monitoring can be a bit tricky since there are few appropriate standards for indoor air quality (IAQ) in environments. There are industrial standards for permissible exposure limits for certain chemicals used in manufacturing and other workplace settings, but there are no standards for indoor levels of molds. This is partly because of great variability in people’s reactions to mold and also because there is no scientific support for designating a particular mold measurement as “safe” or “unhealthy.”

However, where there are known contaminants or hazards present (such as the use of a direct-fired heater that can cause a decrease in oxygen and an increase in carbon monoxide) testing should be routine. These types of hazards may even lead to the use of air monitors and alarms rather than sampling.

Engineering and work-practice controls

Contractors should use a variety of methods to control hazards. Implementing a hazard control program takes a great deal of communication and planning among all affected stakeholders: owners, designers, project managers, site superintendents and safety staff.

Source removal: Identify a source of contamination and relocate it so that it will not affect the IAQ. For example, do not locate a diesel generator or a roofing kettle near a building air intake.

Source substitution: Identify a material likely to impact the IAQ and select a similar but less toxic substitute. Review the manufacturer specifications and consult with safety professionals. For example, choose latex over oil-based paint, hardwood over pressed wood, water-based over solvent-based adhesives, low formaldehyde-emitting fabrics and continuous-filament carpet.

Source encapsulation: Create a barrier around the source and isolate it from other areas of the building so that there is no recirculation of air from the work area into occupied spaces. This may include physically isolating a section of the building with polyethylene sheeting or other barriers as well as isolating the space from the general ventilation system by blocking return air grilles. Keep doors closed and seal stairwells so they do not act as conduits for contaminants.

Ventilation: Use either dilution ventilation or local exhaust ventilation in conjunction with isolation techniques to reduce contaminant levels. Dilution ventilation increases the amount of outside air passing through an area to dilute and flush out low levels of contaminants. If the building ventilation system will be in contact with the work area, consider installing additional filters to keep particulates out of the ductwork.

When strong odors and higher contaminant levels are expected, the area should be encapsulated and placed under negative pressure. This technique isolates the work area from the building ventilation system and uses exhaust fans to directly remove contaminants to the outside. Explosion-proof fans must be used when there are flammable chemicals in the work area. Positively pressurizing nonwork areas and running ventilation systems overnight will minimize contaminant migration into occupied spaces.

Scheduling: It may be possible to minimize worker or occupant exposure to those contaminants by carefully scheduling the work during periods of low occupancy such as holidays, evenings and weekends. In addition, allow for a “flush out” period of ventilation before reoccupying the work area. It is recommended that the area be flushed out with maximum outside air at normal temperatures for 72 hours before re-occupancy. Increased ventilation may also be warranted for two weeks to two months post-occupancy to remove low level off-gassing.

Good housekeeping practices will go a long way toward containing dusts and construction debris and allowing building occupants to feel confident that the project is well-managed. Consider using a HEPA-filtered vacuum cleaner to minimize recirculation of contaminants. Suppress dust with wet methods. Quickly clean up spilled materials. Protect porous materials such as insulation from exposure to moisture and contaminants.

For all construction and renovation dusts, a plan to minimize exposure should be implemented. Appropriate containment should be in place to prevent disbursement into occupied areas.

ASHRAE Standard 62.1 provides guidance for construction in occupied buildings where the work entails sanding, cutting, grinding or generating significant amounts of airborne particles or procedures that can generate significant amounts of gaseous contaminants. Work practices may include mitigating the introduction of contaminants to occupied areas, including sealing the work area with temporary walls or sheathing, air-exhausting or pressurization.

Reporting and responding to complaints

If workers suspect their health problems are caused by construction and renovation exposures in their work areas, they should report concerns immediately to supervisors or the people responsible for building maintenance.

Owners and managers should have a plan in place for responding to IAQ complaints.

This plan should include:

  • Develop a plan describing anticipated work activities and their location, associated source con-taminants and areas potentially affected.
  • Immediate and appropriately respond to worker complaints.
  • Establish clear procedures for recording and responding to IAQ complaints to ensure an adequate and timely response.
  • Identify appropriate resources for response.
  • Provide feedback to owners, work-ers and other stakeholders on response actions.
  • Follow up to ensure that remedial action has been effective.
  • Identify all key personnel who are responsible for addressing con-struction or renovation-related activities and airborne contaminant control.
  • Assure that construction and renovation workers are equipped with necessary personal protection equipment such as N95 (or contaminant-specific) respirators, gloves and eyewear.
  • Schedule construction or renovation work during periods of low building occupancy or when occupants are not in the building.
  • Isolate construction work areas from occupied areas using appropriate containment barriers.

American Society of Heating, Refrigerating and Air-Conditioning Engineers (ASHRAE) — Indoor Air Quality Guide: Best Practices for Design, Construction, and Commissioning

Centers for Disease Control and Prevention — Construction Safety and Health Indoor Air Quality (, and Indoor Air Quality (

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