Safety Report

Ensuring indoor air quality during winter construction

Part one

Construction workers in Alaska can face many challenges, especially during winter. Tight construction schedules and low temperatures contribute to a number of hazards that need to be managed to ensure worker safety.

One of the biggest hazards can be indoor air quality (IAQ) during and after construction. These IAQ hazards can affect workers as well as building tenants. There are many potential contaminants that can affect air quality, some of which can be increased by cold weather construction techniques such as tenting and heating that can create additional hazards.

These can be mitigated by careful planning, exposure assessment, testing, engineering and work practice controls, and good project management.

This information will be presented in two parts in The Alaska Contractor. Part one will cover planning and hazard assessment in this issue, and part two will cover testing and monitoring, engineering and work practice controls, and reporting and responding in the spring issue.


Alleviating hazards actually begins in the design phase before ground is broken. Careful attention to materials and scheduling work flow is the first step.

Planning by designers and project managers, appropriate contract language, material review and selection processes, and effective control strategies combined with proactive communication can successfully control pollutant levels, allay concerns and maintain construction worker and final occupant comfort during and after construction.

Proper construction sequencing is essential to prevent mold, moisture and contamination problems. An example of improper sequencing would be installing drywall that could absorb or retain moisture before the building is dried in, potentially leading to mold growth later. Another example would be operating permanent HVAC equipment during construction that could lead to system contamination.

Unprotected ductwork or improper storage of materials on the job site can also lead to contamination.

Therefore it is essential in the design phase to consider site environmental conditions to reduce the effects of moisture damage and contamination during construction. To avoid contamination of installed products, the entry of construction materials needs to be carefully planned.

For example, it is important to delay the installation of absorptive materials (such as furniture, ceiling tiles or carpet) until high-emission activities (caulking, painting and use of sealants and adhesives) are completed and flush-out is accomplished. If scheduling does not allow for the correct sequencing/timing, then other isolation and protection methods must be employed.

Schedule compression can often lead to IAQ issue magnification, so careful project planning and communication are essential.

Operating permanent HVAC systems should be avoided during construction. This practice can introduce many potential contaminants into the system and building. The ANSI/ASHRAE Standard 62.1 Ventilation for Acceptable Indoor Air Quality provides guidance for use of filters during construction, but even with filters, contamination can occur.

Another factor during the design phase is to schedule the building flush-out after activities with potential IAQ are performed. In some cases, it is reported that this period may need to be extended up to 10 weeks to be successful.

During the design phase, assessment of building materials should also be reviewed. Designers should use products designed and manufactured to produce the least harmful and irritating effects (such as LEED or GREENGUARD standards). For example, health hazards associated with Volatile Organic Compounds (VOC) exposure can be minimized by choosing low VOC-emitting products.

Hazard assessment

Before work commences, the site safety team should conduct a hazard assessment in conjunction with the owner, project manager, designer and site superintendent.

The team should consider all the potential sources of exposure. The most common include:

Particulates: Particulate material such as dusts and fibers are likely to be produced during construction and renovation activities. Sources include nuisance dusts created by cutting, sanding, disturbing dirty areas or the installation of Portland cement, gypsum, limestone, Plaster of Paris drywall, plaster, concrete, soil, wood, masonry, flooring, roofing and duct-work.

Fibers and toxic dusts: Materials that contain fibers such as fiberglass-composite materials or insulation can irritate the skin, eyes and respiratory tract when disbursed in the air and/or inhaled. Toxic dusts containing asbestos, polychlorinated biphenyls (PCBs) or lead can cause serious long-term health effects.

Potential carcinogens: Particulates that are subject to special regulation include lead paint dust, which is toxic to the nervous system, and asbestos, which is a carcinogen. Projects that may disturb lead painted surfaces or asbestos containing materials warrant close supervision

Biological materials: Chronic dampness from water intrusion leads to increased bacteria, mold and other microbes in a building environment. Microbial-contaminated materials require special precautions prior to demolition to prevent biological dusts from dispersing in the occupied space. Another example of biological contamination is an accumulation of bird or rodent droppings. In both cases, uncontrolled disturbances could spread potentially allergenic or infectious dust to occupied building areas.

Volatile organic compounds: VOCs are compounds that are readily released in the form of a gas from building materials. Construction projects may introduce a variety of VOC emitters into a space. These compounds are associated with a variety of health symptoms. At high enough levels, exposure can cause central nervous system effects (headaches, drowsiness). At lower levels, they are reported to be irritants to the eyes, nose and throat. Use of the following categories of VOC-emitters should initiate control strategies to minimize occupant exposures: coatings, stains/varnishes, resilient flooring, caulks, fuels, cleaners, wall coverings, sealants, adhesives, composite wood products, paints, carpeting, fabrics and draperies.

Physical agents: These include noise, vibration and uncomfortable temperatures, which can generate complaints from building occupants working adjacent to a renovation. Construction activities may interrupt heating, ventilating and air conditioning services. Vibration can also contribute to more serious hazards such as the delamination of asbestos material in another space or the creation of a chemical spill when containers fall from shelves.

Combustion sources: These include vehicles, generators and compressors that might introduce carbon monoxide, carbon dioxide, nitrogen oxides and sulfur dioxide into a space. Welding can produce these contaminants as well as ozone. These gases may cause eye, nose, throat and respiratory system irritation. Carbon monoxide exposure may cause headache, dizziness and rapid heartbeat, and at high levels it can be fatal.

Heaters: Temporary heating devices play a large role in winter construction in Alaska. They allow temperature-critical work to be performed and provide a more comfortable working environment. Improper selection and use, however, can lead to serious consequences such as burns, carbon monoxide poisoning, oxygen deficient atmospheres, fires or explosions. The three main categories used are direct-fired heaters (commonly known as salamanders or torpedoes), indirect-fired heaters and electric heaters. OSHA provides some guidance on using these devices (1926.154 - Temporary heating devices).

Part two concludes in the next issue.

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