Furnace Gas Smell Causes | Natural Gas Odor from Furnace
Why furnace smells like gas. Natural gas leak safety, NW Natural procedures, and Portland emergency response.
Read Time
15 min
Service Area
Portland Metro
License
CCB #187834
Owner & Lead HVAC Technician
🚨 NATURAL GAS LEAK EMERGENCY
If you smell natural gas (rotten eggs) from your furnace, EVACUATE IMMEDIATELY. Natural gas leaks can cause explosions and fires.
DO NOT:
- • Use electrical switches or appliances
- • Make phone calls inside the house
- • Light matches, candles, or cigarettes
- • Try to fix it yourself
- • Turn gas off/on at appliance
DO:
- • Leave house immediately
- • Call NW Natural: 800-882-3377
- • Call 911 if CO symptoms
- • Go to neighbor's house
- • Report smell strength and location
A natural gas smell coming from your furnace is one of the most serious emergencies you can face in your Portland home. While natural gas is odorless in its pure form, utilities add a distinctive rotten egg smell (mercaptan) to help detect dangerous leaks. Understanding when a gas smell is an emergency versus normal operation can save lives and prevent catastrophic damage.
In Portland, where NW Natural provides natural gas service to over 750,000 customers, gas leaks from furnaces are taken extremely seriously. The utility responds to emergencies 24/7 and has specific procedures for investigating and clearing suspected leaks before any furnace work can proceed. Knowing how to distinguish between normal pilot light smells and dangerous leaks is crucial for homeowner safety.
This guide covers furnace gas smell causes, emergency procedures, and Portland-specific safety information to help you respond appropriately to this serious situation.
Pilot Light vs. Gas Leak
Brief gas smells during furnace startup are usually from pilot lights and disappear within 1-2 minutes. Persistent smells, especially when furnace is off, indicate dangerous leaks requiring immediate evacuation and NW Natural response.
Common Causes of Furnace Gas Smells
Gas Valve Leak
Faulty gas valve allows gas to escape even when furnace is off
Symptoms:
Gas smell present constantly, even when furnace not running
Danger Level:
High - Can cause explosions if gas builds up
Action: Shut off gas at meter, evacuate, call NW Natural
Cracked Gas Line
Damaged gas piping or fittings leak natural gas
Symptoms:
Strong gas smell, hissing sound near furnace
Danger Level:
Critical - Immediate explosion risk
Action: Evacuate immediately, call NW Natural emergency
Faulty Pilot Light
Pilot light assembly leaks gas when not properly adjusted
Symptoms:
Gas smell during startup, pilot light goes out frequently
Danger Level:
Medium - Can lead to carbon monoxide if pilot goes out
Action: Turn off gas, ventilate, call technician
Heat Exchanger Crack
Cracked heat exchanger allows exhaust gases to enter home
Symptoms:
Gas smell during operation, soot around furnace vents
Danger Level:
High - Carbon monoxide and gas leak risk
Action: Shut down furnace, evacuate if strong smell
Gas Line Corrosion
Old or corroded gas lines develop leaks over time
Symptoms:
Intermittent gas smell, especially in older homes
Danger Level:
High - Chronic leak can build up over time
Action: Call NW Natural for inspection
NW Natural Emergency Response Procedures
Immediate Evacuation
- •Leave house immediately without touching electrical switches
- •Do not use phones, appliances, or light matches inside
- •Take family and pets to a safe distance (neighbor's house)
- •Do not re-enter until cleared by utility
Why: Natural gas is explosive and can be ignited by any spark
Call NW Natural Emergency
- •Call 800-882-3377 from safe location
- •Provide exact address and description of smell
- •Stay on line with operator for instructions
- •Do not return until they arrive and clear the area
Why: Professional gas leak detection and repair required
Carbon Monoxide Check
- •Check CO detector - if alarming, call 911 immediately
- •Seek medical attention if experiencing symptoms
- •Ventilate area only after gas leak ruled out
- •Install additional CO detectors if needed
Why: Gas leaks can also cause CO poisoning without odor
Professional Inspection
- •Wait for NW Natural to clear gas leak
- •Then schedule licensed HVAC technician
- •Do not operate furnace until fully repaired
- •Get written safety certification before use
Why: Ensures all safety systems are working properly
Carbon Monoxide Detectors and Furnace Safety
CO Detector Requirements
- •Install CO detectors on every level of home
- •Place within 10 feet of furnace and sleeping areas
- •Test monthly and replace batteries twice yearly
- •Replace detectors every 5-7 years
- •Interconnected detectors recommended
CO Poisoning Symptoms
- •Mild: Headache, nausea, confusion
- •Moderate: Dizziness, fatigue, chest pain
- •Severe: Loss of consciousness, seizures
- •Emergency: Call 911 immediately if suspected
- •Note: CO is odorless - detectors are essential
Portland Natural Gas Service
800-882-3377
Emergency Gas Leak
503-226-4211
NW Natural Main
24/7
Emergency Response
NW Natural serves Portland metro area with over 750,000 customers. They respond to gas emergencies within 30 minutes and provide free leak investigations.
Pilot Light Smell vs. Dangerous Gas Leak
Normal Pilot Light Smell
- •Duration: Brief (30 seconds to 2 minutes)
- •When: Only during furnace startup
- •Strength: Mild, disappears quickly
- •Action: Normal - no action needed
- •Pilot Status: Blue flame, steady
Dangerous Gas Leak
- •Duration: Persistent or recurring
- •When: Anytime, even furnace off
- •Strength: Strong, doesn't dissipate
- •Action: EVACUATE - call NW Natural
- •Other Signs: Hissing, pilot light out
When in Doubt - Call NW Natural
In Portland, it's always better to call NW Natural emergency line for any persistent gas smell, even if you'
Remember: Natural gas companies would rather respond to unnecessary calls than miss a dangerous leak.
Furnace Gas Leak Prevention and Maintenance
Annual Furnace Maintenance
- •Professional tune-up every fall
- •Check gas valve and connections
- •Inspect heat exchanger for cracks
- •Test gas pressure and pilot light
- •Verify CO detector functionality
Gas Safety Best Practices
- •Never store flammable materials near furnace
- •Keep furnace area clear and accessible
- •Report any unusual furnace behavior
- •Install gas shut-off valve near furnace
- •Educate family about gas smell procedures