• The company's experience with similar problems, including the training and experience of the individuals responsible for the work
• The company's knowledge of local codes and regional climate conditions
• The quality of your interview of the company's representative and the proposal they submit
• The company's reputation
• The cost of the consultation and services provided relative to other bidders 

A U.S. Environmental Protection Agency (USEPA) survey of firms providing IAQ services found that almost half had been providing IAQ diagnostic or mitigation services in non-industrial settings for ten or less years.  

The Interview and Proposal

The following guidelines may help you screen IAQ professionals.
Competent professionals will ask questions about your situation to see whether they feel they can offer services that will assist you.  The causes and potential remedies for IAQ problems vary greatly.  A consultant needs at least a preliminary understanding of the facts about what is going on in your building to determine if the company has the professional skills necessary to address your concerns and to make effective use of company personnel.  Often a multi-disciplinary team of professionals is needed.

A proposal for an investigation should emphasize observations rather than measurements.  Information may be needed in four areas to resolve an IAQ problem:

1) Information that the inspector can gather by looking and asking questions,

2) Use of air samplers and other instruments that may be needed to test air quality,

3) Identification of potential sources of contaminants,

4) How the contaminants could move through the building.

The consultant should discuss the role of environmental monitoring such as the measurement of indoor and outdoor air temperature and relative humidity.  Non-routine measurements (such as relatively expensive sampling for mold or volatile organic compounds) should not be recommended without site-specific justification.

The staff who will be responsible for a building investigation should make it clear to you that they have a good understanding of the relationship between IAQ and a building's structure, its mechanical ventilation systems, and human activities.  For example, a lack of adequate outdoor ("fresh") air is at least a contributing factor in many IAQ problems.  Evaluating the performance of a ventilation system requires an understanding of the interactions among the mechanical system, the number of persons in the building, and what they do there.

Some building investigators may have accumulated a wide breadth of knowledge even if not originally trained in an aspect of building design and operation.  For example, a mechanical engineer and an industrial hygienist generally see buildings differently.  However, a mechanical engineer with several years of IAQ experience may have seen enough health-related problems to cross the gap into the specialty of workplace health and safety.  Likewise, an industrial hygienist with years of experience studying problems in office settings may have considerable expertise in ventilation systems and other building mechanical systems.

Reputation of the Firm

1) Ask any firm you are considering to hire to provide references from clients who have received comparable services.  In evaluating references, it is useful to consider what long-term follow-up the company provided its clients.  For example, after the contract was completed, did the contractor remain in contact with the client to ensure that problems did not recur?

2) Check local consumer protection programs for complaints about the business you are considering.  There are no Federal regulations covering professional services in the general field of IAQ. However, some professions (that is, engineers and industrial hygienists) whose practitioners work on IAQ have mandatory or voluntary state licensing or certification requirements such as those of the state of Texas.  Check if your state has similar requirements for IAQ consultants.

Building owners and managers who suspect that they may have a problem with a specific pollutant (such as radon, asbestos, or lead) may be able to obtain assistance from their city, county, or state health department.  Government agencies and affected industries have developed training programs for contractors who diagnose or mitigate problems with these particular contaminants.

Knowledge of Local Codes and Regional Climate Conditions

Familiarity with state and local regulations and codes helps avoid problems.  For example, in making changes to a ventilation system, it is important to conform to local building codes.  Heating, cooling, and humidity control are different in different parts of the country, and they can affect the selection of an appropriate remediation approach.  Getting assurances that all firms under consideration have this knowledge is particularly important if you must rely on expertise from outside your local area.