A school or clinic odor can come from a dry trap, a seal, drainage or ventilation. Investigate persistent or strong odors promptly and involve building safety or infection-control staff as appropriate. Smell alone does not establish safety; symptoms require occupants to leave the affected area and seek help.
What the smell is
Sewer gas is a mix, and the part you smell is hydrogen sulfide. ATSDR says people can detect it at very low concentrations, roughly 0.0005 to 0.3 parts per million. OSHA lists the odor threshold as low as 0.01 to 1.5 ppm and notes that effects begin around 2 to 5 ppm with prolonged exposure: nausea, tearing eyes, headaches. Odor thresholds do not establish the concentration or safety of an actual hallway exposure; odor alone cannot be used as an exposure measurement.
Why smell is a bad gauge
OSHA says loss of smell can occur at 100 to 150 ppm, and ATSDR says people can lose their sense of smell within minutes at higher levels. A room where the smell suddenly disappears is not proven safe. If anyone reports dizziness, headache or breathing trouble, move people out first and arrange appropriate help. If it is strong, do not wait.
The usual causes
- Floor drains in janitor closets, mechanical rooms and restrooms that were never topped off, especially over breaks and long weekends.
- Sink traps in seldom-used science rooms, exam rooms and lab spaces.
- A blocked vent or damaged toilet seal.
- A break in the drain line under the slab.
The fix
Refill every trap in the affected area, ventilate and recheck. If the smell recurs, a plumber traces the vent and drain lines. Trap primers on floor drains keep the seal up between uses.
The clinical extra
CDC notes that in healthcare facilities, biofilms can grow in sinks and sink traps, and that drains connect to the sewer. A smell from a clinical sink is a cue to involve your infection control staff, not just facilities. Your licensing agency and internal policies set the specific requirements; this page does not replace them.
Documentation
Keep a log of complaints, times and actions. The EPA's building air quality guide includes complaint forms and incident logs built for this. Our property manager odor log has a version to copy. HQ offers 24/7 emergency service, is licensed and insured, and gives free estimates with upfront pricing.