How to tell if you have a gas leak in your furnace?

A gas leak in your furnace typically produces a rotten-egg or sulfur odor near the unit, caused by the odorant added to natural gas. Other signs include a hissing sound near the gas line, dead houseplants near vents, or a pilot light that keeps going out. If you notice any of these, leave immediately, avoid switches, and call your gas utility then a licensed HVAC technician. Home Therapist (HVAC lic. CAC1819196) offers FREE diagnosis on every visit.

What if I smell gas but no leak?

A brief gas odor when your furnace first fires up at the start of heating season is common and usually fades within minutes as dust burns off the heat exchanger. If the smell persists beyond a few minutes, grows stronger, or returns repeatedly, treat it as a real leak: evacuate, call TECO, then call a licensed technician. A lingering smell with no visible leak can still indicate a cracked heat exchanger or a loose fitting that requires professional inspection. Home Therapist provides FREE diagnosis and has 1,300+ five-star reviews across Tampa Bay.

EMERGENCY

Gas Smell? LEAVE + Call NOW

Gas smell = evacuate immediately. Don’t use switches, phones, or appliances inside. Call TECO (813-275-3700) first, then us. 24/7 emergency dispatch. CAC1819196 / CFC1431159.

Call Now: (813) 343-2212

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Quick Answer

Gas smell in Tampa = EMERGENCY. Steps: (1) Get everyone + pets OUT of the house, (2) Do NOT turn on/off any electrical switches (spark risk), (3) Do NOT use phones inside, (4) Leave doors open for ventilation, (5) Call TECO Peoples Gas 813-275-3700, (6) Then call us (813) 343-2212. Common causes: loose pipe fitting, cracked heat exchanger, faulty gas valve, or pilot light issue.

Common Gas Leak Sources

Loose Pipe Fitting

Call a tech

Symptom: Slight odor near gas appliance. Threaded connection loose.

Pro pipe tightening + leak test. $279-$399.

Cracked Heat Exchanger

Call a tech

Symptom: Furnace gas smell + possible carbon monoxide.

Replacement or full furnace replace. $6,000-$12,000. Most serious.

Failed Gas Valve

Call a tech

Symptom: Gas leaks even when unit is off.

Gas control valve $299.

Pilot Light Issue

Call a tech

Symptom: Pilot not burning gas cleanly.

Pilot cleaning + thermocouple $279.

Gas Smell When the Heat Runs: Read This First

Safety comes before everything else here. Natural gas and propane are odorless, so utilities add a chemical called mercaptan that smells like rotten eggs or sulfur specifically so you can detect a leak. If you smell a strong, persistent rotten-egg odor, do not treat this as a repair you research later. Take these steps now:

Get everyone out of the house, including pets.
Do not flip switches, light anything, or use your phone inside. A spark can ignite gas. Leave the door open as you go.
Do not try to find or fix the leak yourself.
From outside or a neighbor’s, call your gas utility’s emergency line and 911. In Tampa Bay that is TECO Peoples Gas at 877-832-6747, or call 911. They will shut off and make the area safe.

Sound familiar? Get a FREE Tampa Bay diagnosis today. Call (813) 343-2212 Book Online

Once the area is confirmed safe by the gas company, that is when a licensed pro diagnoses and repairs the source. Here is how to tell the difference between a true emergency and the harmless smells people sometimes confuse with a gas leak.

Telling a Real Gas Leak From a Harmless Smell

Dust burn-off (usually harmless). The first time you run your furnace or heat strips each winter in Tampa, dust that settled on the heat exchanger or electric elements over the long cooling season burns off. It produces a faint burning or slightly acrid smell for the first 20 to 30 minutes of operation, then fades. This is normal and not a gas smell. If a faint burning odor clears within half an hour on the first heating cycle of the season and never returns, it was almost certainly dust.

Rotten-egg or sulfur smell (treat as a gas leak). A strong sulfur or rotten-egg odor, especially one that gets stronger when the heat runs or that lingers near the furnace or gas line, is the mercaptan warning and must be treated as a leak. Follow the safety steps above.

A different danger: cracked heat exchanger and carbon monoxide. On a gas furnace, the heat exchanger separates combustion gases from the air you breathe. If it cracks (more likely on older or sediment-stressed units), it can leak carbon monoxide, which is colorless and odorless. Warning signs include a stuffy or chemical smell when the heat runs, soot around the furnace, frequent headaches or nausea that improve when you leave the house, and a yellow rather than blue burner flame. Every Tampa home with gas heat should have working carbon monoxide detectors. If a CO detector alarms, get out and call 911.

The only smell on this list a homeowner should wait out is the brief first-of-season dust burn-off. Anything that smells like gas, sulfur, or burning that does not clear, or any CO detector alarm, means leave and call. Then call us for a licensed diagnosis.

How We Diagnose It and What It Costs

Once the gas company has made the area safe, our licensed technicians find and fix the source with the right instruments. Here is where Tampa Bay pricing typically lands in 2026, with FREE diagnosis on every call.

Combustion and gas-leak diagnosis: FREE. We use an electronic gas-leak detector and a combustion analyzer to locate leaks and test for carbon monoxide, and we inspect the heat exchanger.
Gas line or connection repair: $279 to $695 depending on the location and fitting.
Burner, thermocouple, or gas valve service: $279 to $650.
Cracked heat exchanger: on most furnaces this is a safety condemnation. A new heat exchanger is costly and, on an older unit, replacing the furnace is usually the safer and smarter choice. A new Goodman or Daikin gas furnace is quoted in writing after a FREE estimate, and a complete gas furnace system (furnace plus AC) runs $7,986 to $13,209 for Goodman and $9,318 to $13,206 for Daikin Value, depending on size and efficiency.
Carbon monoxide detector installation: quoted with the repair, and worth it on every gas-heated Tampa home.

FREE estimates and FREE diagnosis on every visit. No diagnostic fee. We never cut corners on a gas or carbon monoxide call, your family’s safety is the whole job.

What to Do Right Now

Everyone OUT + pets.
Do NOT use electrical switches.
Do NOT use phones inside.
Open doors if safe.
Call TECO from outside: 813-275-3700.
Then call us 24/7: (813) 343-2212.

FREE diagnosis after gas company confirms safe. Repair varies by cause.

Get a FREE Diagnosis From a Licensed Tampa Bay Tech

No diagnostic fee. No trip charge. We tell you exactly what is wrong and what it costs before you approve anything.

Call (813) 343-2212 Book Online

Available 7 days a week | Same-day service | Licensed & insured

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FAQ

How to tell if you have a gas leak in your furnace?
A gas leak in your furnace typically produces a rotten-egg or sulfur odor near the unit, caused by the odorant added to natural gas. Other signs include a hissing sound near the gas line, dead houseplants near vents, or a pilot light that keeps going out. If you notice any of these, leave immediately, avoid switches, and call your gas utility then a licensed HVAC technician. Home Therapist (HVAC lic. CAC1819196) offers FREE diagnosis on every visit.
What if I smell gas but no leak?
A brief gas odor when your furnace first fires up at the start of heating season is common and usually fades within minutes as dust burns off the heat exchanger. If the smell persists beyond a few minutes, grows stronger, or returns repeatedly, treat it as a real leak: evacuate, call TECO, then call a licensed technician. A lingering smell with no visible leak can still indicate a cracked heat exchanger or a loose fitting that requires professional inspection. Home Therapist provides FREE diagnosis and has 1,300+ five-star reviews across Tampa Bay.

Natural gas smell?

Rotten egg / sulfur (mercaptan is added to natural gas for detection).

Can I try to find the leak myself?

NO. Don’t use any flame or electric tools. Let TECO + us handle it.

Carbon monoxide risk?

Cracked heat exchanger can release CO (odorless, deadly). Get CO detectors if you don’t have them ($30).

Who fixes it?

TECO secures the gas supply. We fix the actual appliance or piping inside the house.

I smell rotten eggs when my heat runs. What do I do right now?

Treat it as a gas leak. Get everyone and pets out without flipping switches or using your phone inside, leave a door open, and from outside call TECO Peoples Gas at 877-832-6747 or 911. Do not try to find or fix it yourself. Once they make the area safe, call us for a licensed diagnosis and repair.

Is a burning smell the first time I turn on heat dangerous?

Usually not. The first heating cycle of the Tampa winter burns off dust that settled on the furnace or heat strips all summer, producing a faint burning smell for 20 to 30 minutes that then fades and does not return. A rotten-egg or sulfur smell is different and should be treated as a gas leak.

What is a cracked heat exchanger and why does it matter?

The heat exchanger keeps combustion gases separate from the air you breathe. A crack can leak carbon monoxide, which is colorless and odorless and dangerous. Signs include a chemical smell with the heat on, soot, a yellow burner flame, or CO-detector alarms. We inspect the heat exchanger and test for CO on every gas-heat diagnosis.

Does Home Therapist handle gas heating and carbon monoxide safety?

Yes. Our licensed technicians carry electronic gas-leak detectors and combustion analyzers, inspect heat exchangers, test for carbon monoxide, and install CO detectors. FREE diagnosis on every visit. For an active strong gas smell, call the gas company and 911 first, then call us at (813) 343-2212. Licensed CAC1819196.