Mold in the Indoor Working Environment

Adopted October 2003 | Updated June 2006

The American Society of Safety Engineers (ASSE), a global non-profit organization, is dedicated to advancing the safety, health, and environmental (SH&E) profession and advancing the technical, scientific, managerial, and ethical knowledge and skills of occupational safety, health, and environmental professionals.

It is ASSE's belief that mold has become an important safety, health, and environmental issue. ASSE members are being asked to respond to mold-related issues including development and implementation of preventive measures and programs, identification and quantification of mold contamination in indoor environments, identification and awareness of worker and workplace activities that increase the potential for exposure to mold, and development and implementation of remediation plans and projects to remove mold from indoor workplaces workplace employee occupants and remediation workers.. With ASSE members conducting such work in the absence of a universally accepted standard from a cognizant authority, ASSE believes the Society can assist its members by providing guidelines under which such work can be executed in a manner that provides protection to workers and which does not cause increased risk to building occupants.

Regarding mold and its potential to cause adverse health effects or aggravate pre-existing conditions, there is some consensus that certain population sectors have a higher risk of such adverse health effects, including the elderly, children, and persons with reduced or compromised immune systems. ASSE's primary focus is worker protection. While ASSE does not in any way discount the need to address the special needs of at-risk populations, the current focus of ASSE's efforts is workplace employee occupants and remediation workers. This position statement is the foundation upon which current ASSE initiatives and efforts in this area will be based and defines ASSE's current understanding and position regarding mold in the indoor environment at this point in time.

What is Mold?

There are many different types of biological organisms and bioaerosols present in the indoor environment. Mold, a group of microscopic fungi, is just one of these types. These spore-producing organisms can thrive in certain indoor conditions - when there is a temperature range conducive to growth, sufficient water or moisture, and a source of nutrients or food. While ubiquitous in nature, excessive mold in the indoor environment can result in offensive odors from the volatile organic compounds released by certain molds during growth and death cycles, and destruction of building components by penetration of the filaments and hyphae produced.

Health Effects

Although current research does not conclusively indicate that mold causes illness in the normal, healthy working population, there is some evidence that excessive exposure to mold may aggravate pre-existing respiratory conditions such as allergic rhinitis and asthma, and may cause allergic reactions in some people. Although adverse health effects related to exposure to mold have been reported, at this time, there is not a conclusive link to pulmonary hemorrhage nor is there conclusive evidence that mold-related illnesses are increasing. Currently there is not consensus among SH&E and healthcare professionals as to the level of mold exposure that is acceptable in indoor environments.

Additionally, to date there is no documentation of universal adverse health effects related to exposure to mold. In contrast, for many hazardous chemicals there are such documented universal adverse effects directly related to certain levels of exposure. For example, any person whose skin comes into contact with concentrated acid will develop a burn and any person exposed to a certain level of nitrogen gas will become unconscious and eventually die.

To further complicate the issue, there are no known mold biomarkers at this time. Biomarkers are chemicals in the body which have a particular molecular feature that makes it possible to measure if an individual has been exposed to disease-causing organisms as well as the progress of any disease resulting from such exposure or the effectives of treatment. Biomarkers are traditionally used to prove correlation between exposure and symptoms or disease.

Those SH&E professionals who are conducting investigation and/or remediation projects are at risk for increased exposure to mold in both quantity and frequency. ASSE recommends reasonably prudent measures be taken to minimize the potential for excessive exposure to mold in buildings.

Standard of Care

Mold assessment and remediation work is being performed and is going to continue to be performed, whether or not there is a consensus standard. Developing guidelines when the adverse health effects of the work environment are not well defined or where the science is still maturing is not a new approach. The approach defined in the 1980s to protect hazardous waste site workers, where the level of required personal protective equipment is based on immediately available direct-read instruments that provide screening results, is just one example. There is a need to move forward with establishing some framework in which workers can be protected from the potential adverse health effects of mold and in which persons needing to address mold-related issues can evaluate any proposed preventive or remediation measures.

Preventive Measures

Regular visual inspections for signs of mold growth and proper building design, operation, and maintenance are key to preventing mold-related incidents in building occupants. Routine measures can be taken to minimize mold growth indoors, primarily by controlling water intrusion into buildings including leaks, condensation, and excessive moisture in outdoor air. Several standards of care from professional organizations exist which address building design and operation, including those developed by the American Society of Heating, Refrigerating, and Air-conditioning Engineers (ASHRAE) and the American Institute of Architects (AIA).

Renovation and remodeling provide the opportunity for unintentional dissemination of previously contained mold contamination if proper containment and decontamination procedures are not developed and implemented. Similarly, such projects provide the opportunity to select construction materials and systems that allow for ready visual inspection and ease of access and maintenance in light of the current concern regarding mold and biological contamination.


There are several key indicators that the level of mold present in a building may be a problem:

  • When there are obvious and hidden causes of excess moisture such as roof and water leaks, humid conditions, lack of positive building pressurization, and improper or compromised vapor barriers
  • When there are complaints of musty odors or visual signs of mold growth

When assessing a building, it is critical to identify and understand:

  • How the building is currently operating with respect to heating, ventilating and air-conditioning
  • Any patterns or cycles of complaints
  • Visual signs of uncontrolled moisture incursion or mold growth

Sampling and Testing

Currently there are no universally accepted standard procedures for sampling of or testing for mold in the indoor environment. In the absence of health complaints or potential or pending litigation, it is more prudent to remediate any identified mold problem rather than to conduct extensive testing to determine the species and concentration of the mold contamination.

However, when situations warrant sampling and testing, such as the need to confirm the presence of mold for litigation or insurance claims, to determine potential worker or building occupant exposure, or to verify the effectiveness of remediation efforts, SH&E professionals should take care to ensure their sampling, testing, and analysis is unbiased and reproducible. Additionally, measures should be taken to minimize the potential for sampling and testing procedures to increase the exposure of building occupants, workers, and the SH&E professional to any mold present in the building.

When interpreting the results of analytical testing, the species present, the ranked order of species, and the total measured concentration in concurrent indoor and outdoor samples need to be considered. Any of the following conditions may indicate there is excessive mold growth in the indoor environment:

  • There are different mold species identified in outdoor versus indoor samples
  • The ranked order in which species are found varies between outdoor and indoor samples
  • There is a significant increase in the concentration of one or more species of mold found in indoor samples when compared to outdoor sample levels

Minimizing worker exposure to mold

There are workplace situations and activities that have the potential to expose workers to mold. Employers and workers need to be aware of such situations and be able to identify activities that may result in increased potential for workers and building occupants to be exposed to excessive levels of mold. Awareness training that provides workers with the knowledge and skills needed to identify potential mold contamination and situations that could require remediation may be needed, as identification of and responding to mold-related situations may well be a new area of activity for workers. Such awareness education should include, at a minimum, information regarding:

  • Conditions that promote mold growth (e.g., temperature, humidity, moisture)
  • Procedures for reporting suspected mold growth by building occupants and workers
  • Recognition of situations and conditions that are outside the limits of the workers' ability to respond and address in a safe manner (e.g., identification of situations that may require additional professional intervention and assistance)
  • Work activities that have the potential to increase worker or building occupant exposure to mold or have the potential to spread any existing mold contamination


Different situations require different approaches and responses. A preventive approach to remove mold when first identified would be different from a situation where there is pending litigation and/or liability issues. Remediation efforts, when undertaken, should include measures to protect the remediation workers and the workers in the building and minimize the potential spread of the contamination. The primary rule should be "do no harm". Key considerations include:

  • Assessing the situation and determining the appropriate response or level of remediation
  • Using methodologies to minimize the potential to increase airborne concentrations of mold such as containment and/or isolation of remediation areas
  • Ensuring proper removal, transportation, and disposal or cleaning of any contaminated or water-damaged materials
  • Repairing the defects or correcting the conditions which led to the problem, generally water intrusion and/or accumulation, water-damaged materials, and/or elevated humidity, in conjunction with, or prior to, remediation
  • Establishing a process to ensure proper maintenance and operation of HVAC and related building systems that may have an impact on water incursion within the building envelope
  • Applicability of, and conformance with, appropriate building codes and recognized engineering codes of practice and nationally recognized consensus standards
  • Limitations on the use of disinfectants or biocides for remediation purposes, as such materials can pose health concerns for the remediation workers and for the building occupants

There are a variety of currently available standards and guidelines published by different agencies and organizations, such as the New York City Department of Health, which are sound references for SH&E practitioners. However, there is not, at this time, one universally accepted consensus standard that can be held as the Standard of Care. To this end, ASSE petitioned the American National Standards Institute (ANSI) to be the secretariat of a standard committee to address worker safety and health during mold remediation projects. This petition was approved by ANSI, and ASSE is now the Secretariat of the Committee for ANSI Z690 Standard "Guidelines for Mold and Fungi Control and Remediation for Worker Protection in Indoor Work Environments.".

Training and Certification

SH&E practitioners who are certified by nationally-accredited professional bodies with a code of conduct or ethics are bound to not practice in any area where they do not have expertise and/or training. Hence, use of a certified SH&E professional carries additional assurance that the work being performed will meet currently acceptable standards, as recognized by other professionals in this practice area.

When it is determined that remediation is needed, selection of persons to perform the remediation, whether using building staff or outside contractors, should include consideration of the person's training and qualifications in this area. Workers should have completed training in mold remediation procedures, including protective measures for workers and building occupants, appropriate for the project being initiated.

Ongoing ASSE Initiatives and Efforts

To assure that the SH&E professional is well informed on mold-related issues, ASSE has undertaken and will continue to:

  • Participate on national voluntary consensus standards committee such as the ASTM E50 Committee on Environmental Assessment.
  • Provide leadership as the Secretariat of the Committee for ANSI Z690 Standard "Guidelines for Mold and Fungi Control and Remediation for Worker Protection in Indoor Work Environments." The purpose of the standard is to establish minimum requirements and recommended procedures to be implemented by employers to minimize employee exposure to mold. The standard does not pertain to vehicles, agricultural operations, or other settings that already have established voluntary national consensus standards. The proposed standard does not establish an exposure level or action level for identification purposes or to trigger remediation activities.
  • Work at both the federal and state levels to ensure that legislators interested in addressing mold understand both the appropriate response to mold risks and the appropriate SH&E training and experience needed to meet those risks, as ASSE has done in addressing federal legislation by Representative John Conyers (D-MI).
  • Prepare technical information about mold-related issues based on good science and sound technology
  • Be proactive in protecting the interests of SH&E professionals in addressing legislation, regulation, and overall public policy issues at the national, state, and local levels
  • Strongly support the concept that any certification body recognized in legislation or regulation to address mold identification and remediation be accredited by a nationally recognized accrediting body such as the National Commission for Certifying Agencies [NCCA] or the Council of Engineering and Scientific Specialty Boards [CESB]
  • Provide leadership in the protection of workers' safety and health from potential mold hazards
  • Promote awareness of worker protection issues and appropriate and safe work practices through publications, presentations, and research.

Mold in the Indoor Working Environment

Approved 10/03 by the ASSE Board of Directors
Updated 6/11/05 by ASSE Government Affairs Committee

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