Many homeowners assume their carbon monoxide (CO) detector will alert them to any dangerous gas in their home, but this is a potentially dangerous misconception. The short answer is no - standard carbon monoxide detectors cannot detect natural gas (methane) or propane leaks.
Key Differences Between CO and Natural Gas
| Characteristic |
Carbon Monoxide (CO) |
Natural Gas (Methane) |
| Source |
Incomplete combustion of fuels |
Pipeline gas, appliances |
| Color |
Colorless |
Colorless (but odor added) |
| Smell |
Odorless |
Rotten egg smell added |
| Density |
Similar to air |
Lighter than air |
| Primary Danger |
Poisoning |
Explosion/Asphyxiation |
Why CO Detectors Don't Detect Natural Gas
Carbon monoxide detectors use specialized sensors (typically electrochemical) designed specifically to detect CO molecules. They cannot detect other gases because:
- Different sensor technology: CO sensors react to carbon monoxide's unique chemical properties
- Different alarm thresholds: Dangerous CO levels (50 PPM) are much lower than explosive gas concentrations (20,000 PPM for methane)
- Different detection purposes: CO detectors warn of poisoning risk, not explosion risk
Important: The "rotten egg" smell added to natural gas isn't reliable protection. Some people can't smell it (olfactory fatigue), and the odorant can dissipate over time or be absorbed by materials in your home.
For complete protection, consider these detector types:
- Natural gas detectors: Specifically detect methane/propane leaks
- Combustible gas indicators: Detect a range of flammable gases
- Combination detectors: Some models detect both CO and combustible gases
- Smart gas detectors: Can send alerts to your phone when away from home
Where to Place Gas Detectors vs CO Detectors
| Detector Type |
Ideal Placement |
Reason |
| Carbon Monoxide |
Breathing height (5ft), near bedrooms |
CO mixes evenly with air |
| Natural Gas |
Near ceiling, above gas appliances |
Methane rises toward ceiling |
| Propane |
Near floor, in basement if applicable |
Propane sinks toward floor |
When You Might Need Both Detectors
Consider installing both types of detectors if your home has:
- Gas appliances (furnace, water heater, stove)
- Attached garage (vehicle exhaust contains CO)
- Fireplace or wood stove
- Older gas lines or appliances
- Propane tanks for heating or cooking
Safety Tip: Combination CO/explosive gas detectors are available, but read specifications carefully. Some "combo" detectors only monitor for CO and one type of flammable gas.
What to Do If You Suspect a Gas Leak
If you smell gas or suspect a leak:
- Leave immediately - Don't try to locate the source
- Avoid creating sparks - Don't turn lights on/off or use phones
- Call for help from outside - Contact gas company or 911
- Don't re-enter until professionals declare it safe