A building’s indoor air quality (IAQ) can be impacted by internal and external workplace odors including odorous byproducts of mold.

Common Workplace Odors

Dry Sink and Floor Drain P-traps

The P-trap is a plumbing device that is attached to a sink or floor drain and prevents odorous plumbing and sewer gases from passing into the building space. A dried P-trap is the most common odor source in campus buildings. Odors are often characterized as “rotten eggs” or sewage. Odors are intermittent and may be very strong at times.

In a laboratory, negative air pressure ventilation is more likely to pull up odors from a drain than an office (which has positive pressure ventilation). Dry traps could occur in “cup sinks” (small sinks in the middle of lab benches), floor drains, and sinks covered by equipment or no longer used. Prevent or eliminate dry trap odors by running water in all sinks with a ½-gallon of water once a month.

Office Remodeling

Primer, paint, and new furnishings (e.g., carpet, laminate flooring) can emanate odors locally and be distributed through the ventilation system. Campus projects use low-odor materials in most cases, but trace odors like a “new car smell” may still be detected by building occupants after the work is completed, and may take some time to dissipate. Maximize air circulation with continuous air circulation until the odors are satisfactory.

Plug-in Scented Oil Air Fresheners

These devices are discouraged in the work environment because they may contain chemicals that may cause eye and respiratory irritation.

Spoiled Food

Look for spoiled food in offices and refrigerators, and discard promptly. Check refrigerators periodically and keep clean.

Laboratory Chemicals

Laboratories are designed to maintain a negative pressure between the laboratory and adjacent non-laboratory spaces. This pressure differential prevents uncontrolled, odoriferous vapors from leaving the laboratory and migrating to the surrounding areas such as hallways. To minimize malodors, follow best laboratory work practices and keep the laboratory door closed.

Odors Entering the Building

On occasion, diesel exhaust from stationary generators, delivery trucks, or construction equipment may penetrate buildings. Smoke from on-campus barbeques may also enter buildings. These are normally short-lived events. Close exterior doors and windows. Ask drivers parked near your building’s fresh air intake to turn off their engines. Talk to your building manager if the problem persists.


As of January 1, 2017, smoking is prohibited in all indoor and outdoor facilities on university-owned and leased property with no exception, including vehicles parked on those properties. However, renegade smoke from passersby may migrate into first floor areas through open portals (e.g., doors, windows, and air intakes).

Additional Steps

  • Notify FMS Customer Service at (213) 740-6833.
  • Notify your supervisor of any persistent odors.
  • Contact EH&S at (323) 442-2200 to report any indoor air quality (IAQ) issues.

Mold Prevention

Mold is the name given to a group of fungi that are commonly found on wet or damp building surfaces. These molds are found in the soil and adapt successfully to grow on a wide variety of construction materials and fabrics.

How does mold get into a building?

Mold and fungal spores are everywhere. They occur naturally outdoors, need moisture to grow, and gravitate to areas where there is water damage, elevated and prolonged humidity, or dampness. Common sources of excessive indoor moisture that can lead to mold problems include:

  • Roof leaks from damaged roofing materials, or blocked gutters
  • Storm‐driven rain through window frames, exterior walls, or door assemblies
  • Leaking or broken water pipes, sewer back‐ups, or overflows
  • Damp basements due to poorly managed rainwater drainage or inadequate air circulation
  • Condensation on cold surfaces

NOTE: In the past, plastic tubing connections to water-cooled equipment in unversity labs or shops would regularly pop off during non-peak hours due to rising water pressure. Closed-loop cooling baths have replaced the direct connections to water lines preventing flooding and water damage to labs, offices, equipment, and furniture.

How can mold be prevented?

The key to preventing and stopping indoor mold amplification is to control excessive moisture and condensation.

It is important to keep the susceptible areas in the building clean and dry. In general, mold will not grow indoors without water, dampness, or excessive moisture. If mold is discovered, report it to EH&S at (323) 442-2200 or injuryprevention@usc.edu.

Steps to Take

  • Maintain indoor relative humidity levels below 60%.
  • Ensure the ground slopes downward and away from the building foundation.
  • Check landscape irrigation to ensure the water spray pattern is not contacting the exterior walls.
  • Keep air conditioner drip pans and drain lines clean.
  • Ensure cold storage door latches and gaskets are in good condition.
  • In case of floods or leaking pipes, remove any standing water promptly.
  • Dry out and clean water-damaged materials, or if heavily damaged, remove and replace.
  • Discard materials that are wet for more than 48 hours since they are likely to produce mold growth.
  • Consult with a commercial restoration company immediately in instances where the water damage is extensive.

Additional Information