When should you evacuate a building for a sewer smell?

Any one of these is enough:

1. 1The smell is strong or getting stronger. OSHA says the rotten-egg smell becomes more offensive at 3 to 5 ppm, and people notice it far lower than that. A smell that fills a room or a hallway is more than a dry sink trap.
2. 2Anyone has symptoms. Headache, dizziness, nausea, stinging eyes, coughing or drowsiness in more than one person, especially in the same area, points to real exposure.
3. 3A strong smell suddenly goes away. OSHA warns that at high levels the sense of smell can shut off, sometimes instantly. A smell that was overpowering and now seems gone is a reason to leave, not relax.
4. 4It might be natural gas. Southwest Gas adds a rotten-egg odorant to natural gas, so the two can smell alike. Near a water heater, a stove, a boiler room or the gas meter, treat it as a gas leak.
5. 5It's coming from a pit, vault or manhole. OSHA names manholes, sewer lines and low, enclosed spaces as where hydrogen sulfide collects. A strong smell from an ejector room or lift station is a confined-space problem.

Move people first and make calls from outside. The order below keeps anyone from making a bad situation worse.

1. 1Get everyone out and leave doors open. Southwest Gas's steps for a gas smell say to exit immediately, tell others to leave and leave doors open.
2. 2Make no sparks. Don't flip light switches, thermostats or appliance controls, and don't use matches or lighters. Both Southwest Gas and Wisconsin say this.
3. 3Call 911 from outside. If it may be natural gas, also call Southwest Gas at 877-860-6020, day or night.
4. 4Account for everyone. Check restrooms, storage rooms and any below-grade space. Children and pets are at more risk near the floor, as sewer gas and kids or pets explains.
5. 5Never go back in for someone who collapsed. OSHA says never attempt a rescue in an area that may contain hydrogen sulfide without respiratory protection and rescue training. Tell the 911 dispatcher exactly where the person is.
6. 6Stay out until the fire department clears it. Don't let staff or tenants drift back in because the smell "seems better." See sign 3.

### What the fire crew needs from you

OSHA says first responders must be trained and properly protected before entering areas with elevated hydrogen sulfide, which is why they bring breathing equipment and why you shouldn't go back in. What speeds them up is information. Tell the crew where the smell was strongest, whether anyone had symptoms and where, and where the sewage ejector room, lift station, grease interceptor or gas meter is. Have keys ready for pump rooms and roof access.

### After the all-clear

The smell leaving isn't the same as the problem leaving. Once the building is cleared, have a plumber find the path the gas took, whether that's a dry trap, a failed toilet seal, a broken vent or a leaking pit cover. If the space is a workplace and staff want proof it's safe, an industrial hygienist can measure the air and put it in writing. See who can test a building for sewer gas in Arizona.

Plenty of sewer smells are a nuisance, not an emergency. If the odor is faint, it's near one drain or one restroom, nobody feels sick and there's no gas appliance nearby, you can usually handle it in place:

• Open windows or run the exhaust fan.
• Pour water into every little-used drain: floor drains, mop sinks, spare restroom sinks and showers. Wisconsin says keeping water in the traps stops them from drying out.
• Check that the smell fades once the traps hold water again. Our page on how long a sewer gas smell takes to go away covers airing the space out.

If it comes back, the cause is something water won't fix, such as a blocked vent, a failed toilet seal or a cracked line. Sewer gas smell in a commercial building and why a restaurant smells like sewer cover the usual causes.

Use this when a report comes in and you need to decide fast. When a row doesn't fit, pick the safer one.

Write the plan down before you need it. Decide who makes the call to clear a floor, where people gather, who phones 911 and who meets the fire crew with keys to the ejector room and roof. Log each odor complaint with the time, place and what people felt, because repeat complaints from the same suite point a plumber straight at the cause.

### Three building examples

These are made-up examples to show the decision, not real events.

A restaurant back kitchen at opening. A cook notices a sewer smell by the floor sink under the prep table. Nobody feels sick, and the smell fades after the floor drains get a bucket of water. No evacuation. Log it, and if it returns, have the trap and the grease interceptor checked. See why a restaurant smells like sewer.

An office floor after a weekend. Several employees on one side of the building have headaches by mid-morning, and the smell is strongest near a restroom that shares a wall with the pump room. Clear that side of the floor, call 911 and keep people out of the pump room.

An apartment corridor. Tenants report a strong rotten-egg smell near a vacant unit and the gas meters. It could be dry traps in the vacant unit, or it could be natural gas. Treat it as gas: clear the corridor, make no sparks, call 911 and Southwest Gas.

If staff will go into a pit or vault once the building reopens, OSHA says the air must be tested first by a qualified person. See do I need a hydrogen sulfide detector and OSHA's limits for hydrogen sulfide. For a pit that keeps smelling, read why an ejector or lift station pit smells. For personal symptoms, see the first signs of sewer gas poisoning.

HQ Plumbing is licensed and insured and offers 24/7 emergency service. Once the building is cleared, we find and fix the trap, vent, seal or line behind the smell.