Most of the time we think about indoor air quality (IAQ) problems in terms of buildings that are already completed and occupied. Those problems may consist of mold growth and/or improper ventilation. But have you ever thought about the kinds of IAQ problems that can occur in buildings that may be occupied but are still under construction?

The Sheet Metal and Air Con-ditioning Contractors’ National Association (SMACNA) says there are real problems that can happen, and the organization would like contractors to take the necessary precautions when working in an occupied building.

SMACNA’s book, IAQ Guidelines for Occupied Buildings Under Construction, encourages contractors to take a look at the construction process ahead of time and to plan every step of the way with IAQ in mind.

Filling a Need

SMACNA decided to produce this guideline after members attended an ASHRAE meeting several years ago. At that conference, Bill Navas, project manager, SMACNA, says they could see from a large cross-section of the construction industry that there was a huge need for an organized set of guidelines for occupied buildings under construction.

“There’s plenty of guidance for buildings under operation; ASHRAE has standards. But the situation during construction is very specialized. It presents some very unique problems. And really, the available information is only in the way of the experience factor. Contractors who are experienced in construction recall cases of what they have seen and react accordingly,” says Navas.

The book, which was written under SMACNA’s Building Services Committee, brings together the knowledge from various experiences in order to give readers valuable guidance on how they should proceed.

It is well known that certain construction processes create certain pollutants and that certain situations could be annoying to people who are already occupying a building. Navas notes that there are usually two cases in which these construction processes can create a problem:

1. When a building is partially under construction because it’s in the process of being completed; and

2. When the building is already in operation but portions of it are taken out for construction.

Several states have already adopted the organization’s guidelines, Massachusetts being the most recent. In that case, the Department of Public Health noted several problems with air quality in Massachusetts’ public schools when renovation projects were in progress.

The result is that the Department of Public Health has requested that the Department of Education mandate the application of the SMACNA publication by all contractors bidding for construction projects.

Dust Is An Issue

The book notes that several types of airborne contaminants can occur in a building under construction. The first is dust, which will find its way all over the building unless properly contained. The second source of pollutants involves odors or dust that are involved in the construction process (coatings, adhesives, etc.).

The third source includes emissions produced from equipment used during construction. The fourth category comes into play when damage to existing building systems (demolition of ductwork, etc.) occurs and results in the release of contaminants, such as dust, steam, or natural gas. The final source of pollutants includes those released from waste construction materials that are being stored or transported.

For hvac contractors, dust is probably the biggest issue. That’s because the hvac system itself is often the way in which many pollutants, including dust, are circulated throughout a building. These pollutants can enter a building through return grilles, through the mechanical room, through hvac system intakes, and via temporary or permanent cross-connections.

While dust can never be contained completely, the book points out ways in which the hvac contractor can keep it in check.

Contractors should start by making sure they don’t contaminate the ductwork with dust in the first place. Therefore, one of the steps involves the registers being sealed. Once dust gets into the ductwork, there are two problems:

1. If the system is operational, dust is being moved everywhere in the building.

2. If the system isn’t operational, once it starts up, the dust will cover all the furnishings.

It’s also important that contractors understand how the hvac system works — where it runs from and to — so that if somebody needs air conditioning in a certain area of the building or on a certain floor, they know how to get air to the occupants without getting pollutants from the construction area to them.

SMACNA’s goal in writing the book was to provide an easy-to-use reference guide for contractors, building owners, architects, and anyone else involved in construction of occupied buildings. Some of that reference material answers these questions:

  • What are the most common sources of airborne contaminants?
  • What IAQ control measures can be effective?
  • How can a construction project be planned for good IAQ?
  • How can a site be monitored for compliance with IAQ requirements?
  • As Navas notes, this is not rocket science. “Construction people know exactly what the problems are going to be, so the important thing is to plan ahead of time as to the types of controls that they’re going to exert over the construction process so as to limit or avoid creating hazardous conditions for occupants. Sometimes it’s just an annoyance. Sometimes it’s a very serious thing.”

    To order SMACNA’s IAQ Guidelines for Occupied Buildings Under Construction, call 703-803-2989, or visit the organization online at The list price for the manual is $83, and the discounted price for architectural and engineering firms, government organizations, and schools is $58.

    Publication date: 02/12/2001