Welcome to the State of California 

Hiring Guidance

1. What Can an IAQ Consultant Do?

IAQ consultants vary in their education, training, and experience. For example, a consultant may be an architect, engineer or heating and ventilation specialist, occupational health or medical professional, microbiologist, toxicologist, ergonomics expert (someone who knows how to design a workplace to suit the user), or a licensed industrial hygienist or member of an environmental health and safety association. The ideal consultant for you has a basic understanding of all of the above areas and specialized knowledge in the particular issues of concern in your indoor setting.

Below are descriptions of several types of professionals and how they can help with IAQ problems:

Industrial Hygienists

The role of an industrial hygienist is to protect the health and safety of workers and the community. Most industrial hygienists have college degrees in engineering or the natural sciences, such as biology, chemistry, biochemistry, or microbiology. This education is supplemented by specialized training to evaluate environmental factors that affect health and comfort. Industrial hygienists are key members in most IAQ investigations and can help you determine when the input of other professions is needed.

Mechanical Engineers and Contractors

Engineers are invaluable in understanding the intended design and operation of Heating, Ventilation, and Air Conditioning (HVAC) systems. An engineer's input is essential when it comes to changing existing HVAC systems to improve IAQ. Many mechanical contractors (non-engineers) are helpful in implementing changes to air-handling equipment, but may not have the mechanical engineering background required to design effective solutions.


An architect can help you understand how building design can affect IAQ. Architects also are responsible for specifying interior building finishes and building components, which are part of the total IAQ equation. Look for an architect with formal training or experience in preventing IAQ problems.

Medical Professionals

Occupational physicians and occupational health nurses have specific training in aspects of the work environment and can help IAQ investigators target potential sources of health complaints. An occupational physician should be consulted whenever a specific disease (such as asthma or Legionnaires' disease*) is associated with a particular building or workplace.
*Legionnaires' disease is an infectious disease caused by bacteria belonging to the genus Legionella. Patients with Legionnaires' disease usually have fever, chills, and a cough, which may be dry or may produce sputum.

Other Professions

Building occupants often report nonspecific symptoms, such as headaches, eye discomfort, or muscle symptoms. Although occupants may identify these symptoms as being related to building air quality, some of these reports may actually be associated with improper lighting, noise, poorly designed work stations, or overall job dissatisfaction. Many industrial hygienists can assess and resolve most lighting, noise, and ergonomic (that is, workstation or equipment-use) problems. If such problems require additional expertise, an industrial hygienist can refer you to illumination engineers, acoustics specialists, or professional ergonomists.

The Indoor Air Quality Team Approach

In larger IAQ assessments, it is important to form a team of professionals drawn from the appropriate disciplines. Through their professional training and typically broad practical experience, industrial hygienists generally are familiar with the team approach.

If lack of time or resources prohibits forming a team, you may need to identify a more experienced industrial hygienist to investigate and recommend how to resolve your indoor problem. 

2. How Do I Select an IAQ Consultant?

Most of the criteria used to select an IAQ professional are similar to those you would use for other consultants:

  • 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.

3. Where Can I Find Referrals to IAQ Consultants?

You may be able to find help by looking in the yellow pages of your telephone book (that is, under "Engineers," "Environmental Services," "Laboratories-Testing," or "Industrial Hygienists"). City, county, or state health or air pollution agencies may have lists of firms offering IAQ services in your area. It also may be useful to seek referrals from other building management firms. Professional associations also may have lists:

  • American Industrial Hygiene Association (AIHA),
  • National Air Duct Cleaners Association (NADCA),
  • National Air Filtration Association (NAFA),
  • American Society of Heating, Refrigerating and Air-Conditioning Engineers, Inc. (ASHRAE),
  • Air Conditioning Contractors of America (ACCA),
  • Controlled Environment Testing Association (CETA),
  • Associated Air Balance Council (AABC).

4. After I Hire an IAQ Consultant, What Then?

For property managers, once you have chosen your consultant, it is up to you to make sure the occupants are kept informed of progress on the problem and that they are involved in the process. Occupant involvement enhances credibility and helps to ensure success. It is important to communicate accurately the timing and status of environmental inspections, surveys of the occupants, and sampling results. Communicating the limitations of current knowledge will help establish realistic expectations. Drawing from their experience, many consultants can help you develop credible information for distribution.

Once you receive an IAQ report, read it carefully, especially the conclusions and recommendations. Such reports should include

  • A summary of the evaluation, including a summary of applicable regulatory requirements,
  • An outline of the procedures used during the evaluation,
  • Findings, including laboratory analyses, recommendations and conclusions, cost estimates, and an approximate timetable for corrections of problems that were identified.

It will often not be feasible to implement all recommendations at once, so prioritize your planned response in a manner that suits the seriousness of the situation and available resources. You may be called upon by upper management, building occupants, or a regulatory agency to justify your actions or inaction. Try to get the support of all involved parties by informing them, stage-by-stage, of your progress.

5. How Much Should I Expect to Pay?

Costs for professional services vary greatly given the wide scope of the services that may be required. If unforeseen expenses arise during an investigation, your consultant should clear them with you before proceeding and be able to justify the added cost.

A number of factors determine the cost of a consultation, including:

  • The overall complexity of the problem
  • The size and design of the building and its HVAC system
  • The quality and extent of record that building staff and management have kept
  • The type of report or other summary that is required
  • The number of meetings that are required (formal presentations can be quite expensive)
  • Sampling (that is, use of instruments, personnel to collect samples, and laboratory analyses).

Ask your consultants to estimate costs for investigations of varying depth.

6. CDPH Search for Consultants

Consultants can be found by location, specialty, or both.


This list is provided by the California Department of Public Health (CDPH) Indoor Air Quality Section as a service to the public and to aid those who want to hire professional assistance in addressing IAQ problems. The information presented in the list is "self-reported" by the listed firms, and its accuracy is not verified by the CDPH. Currently, there are no State regulations or certification for contractors conducting most IAQ-related services. Firms included on this list are in no way endorsed or certified by the CDPH.

Last modified on: 4/19/2014 8:59 AM