Health & Safety Project

Odor Complaint Response and Assessment

National Healthcare Services Provider Florida

Solution Overview

Summa canisters used part of the IAQ study where Apex collected indoor and outdoor air samples for volatile organic compounds.


National healthcare services provider

Business Challenge:

  • A healthcare facility’s occupants noticed a strong smell and began complaining about physical symptoms associated with the smell.
  • No one could pinpoint the source or cause of the odor.


  • Apex performed a series of indoor air quality tests to identify the source of the odor, which was determined to be mothballs (naphthalene) placed by the building’s facility manager to ward off rodents and birds.


  • Apex oversaw the removal of the mothballs and performed actions to reduce the concentration of naphthalene in the indoor air.
  • Actions facilitated re-occupancy and the continuation of normal business operations.


A confidential healthcare company engaged Apex to conduct an indoor air quality (IAQ) study at its healthcare facility in Florida after the methods used to remove birds that had entered through a roof hatch caused a strong chemical odor and concern for the health of its staff and patients.


Testing and investigation determined that the source of the odor was associated with mothballs that had been placed by the property manager in the healthcare facility’s drop ceiling (unbeknownst to the client) on the incorrect assumption that they would repel future avian and potential rodent infestations. The mothballs were purchased at a local hardware store and, in subsequent review of the product manufacturer’s safety data sheet (SDS), contained greater than 99 percent naphthalene. The mothballs were deployed just prior to a long holiday weekend. When employees and patients returned to the healthcare facility they complained of an unusual odor. Several employees later refused to work and complained of headaches, eye, and throat irritation.

As part of the IAQ study, Apex collected indoor and outdoor (for comparison) air samples for a broad range of volatile organic compounds (VOCs) using Summa canisters and laboratory analysis via US Environmental Protection Agency (EPA) Method TO-15. The air analysis detected concentrations of naphthalene indoors at several orders of magnitude above the outdoor (background) concentrations. Indoor air concentrations of naphthalene approached 1,000 micrograms per cubic meter of air (μg/m3). Concurrently, outdoor air was found to contain <0.18 to ~1.0 μg/m3 naphthalene.

In consultation with the client’s corporate risk management, the healthcare facility was closed to allow remedial action to dispose of the mothballs and take actions to improve the IAQ. The mothballs were found to have been placed in random locations throughout the ceiling and insulation above the drop ceiling. A restoration contractor was retained to initiate remedial actions. Air scrubbers were deployed to create aggressive fresh air exchange and circulation; greater than eight air changes per hour were maintained continuously.

The entire drop ceiling and insulation above the ceiling were removed to eliminate all of the mothballs, and HVAC units were cleaned; air sampling was then conducted to evaluate conditions. A noticeable mothball odor was still present. Air sampling for naphthalene still found indoor air concentrations at orders of magnitude above concurrent outdoor air.

Apex conducted further testing of building materials to evaluate possible secondary sources for naphthalene off-gassing. Our laboratory consultant conducted special chamber analysis of building materials to evaluate if naphthalene was off-gassing. Bulk samples of wallboard were containerized and placed in the laboratory chamber and allowed to off-gas for 24-hours and airborne VOCs determined via EPA Method TO-15. Bulk samples were evaluated both at room temperature and when heated to 120 F. Chamber analysis confirmed gypsum wallboard throughout the facility was offgassing naphthalene, at concentrations similar to concurrent indoor air concentrations of naphthalene at that time. It is assumed the wallboard had absorbed naphthalene as a result of the mothball deployment. Control samples of wallboard from identical and nearby facilities found no detectable concentrations of naphthalene from similar chamber tests.

Forty days after the mothballs were deployed, the indoor air concentrations were still greater than 10 times the concurrent outdoor air naphthalene concentrations. Given that the mothballs had all been removed and the wallboard assumed to have absorbed naphthalene, additional aggressive fresh air ventilation was required.


In consultation with the client’s corporate risk management and health care professionals, Apex’s senior Certified Industrial Hygienist (CIH) established an acceptable re-occupancy criterion for indoor air. Naphthalene exposures can elicit an acute response and are also a possible carcinogen. Because the populations that frequent the facility included higher at-risk occupants with numerous underlying medical conditions and other sensitive populations, the Agency for Toxic Substances and Disease Registry (ATSDR) and the EPA regional screening levels were the primary sources for establishing acceptable indoor air criteria.

Apex developed a remedial action plan that included aggressive air scrubbing and fresh air circulation. Several rounds of indoor air testing demonstrated that naphthalene had eventually reduced from near 1,000 μg/m3 indoors to about 1.0 μg/m3 in concentration. After three months, indoor air concentrations were reduced to an acceptable level to allow re-occupancy, and the client was able to reopen the facility with the peace of mind that any risk to its patients and staff had been eliminated.

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