It’s not unusual for central heating or cooling system to smell a bit musty when it cycles on for the first time in a season, but some odors can indicate a serious problem. Causes can range from an easy-to-fix clogged air filter to a dangerous gas leak that requires emergency attention. When you notice a smell that you can’t easily identify, these tips can help you locate the source of the odor.
Natural Gas Odors
Natural gas is a combustible substance that can cause fire and explosions. If your home or business has gas service and you smell its characteristic sulfur-like odor, check the pilot lights on your gas-powered appliances and heaters to ensure that they are lit. If the pilot is out, shut off the equipment’s gas valve and wait five minutes for the gas to disperse before attempting to relight the pilot. If the smell of gas persists, open your doors and windows, evacuate the building and call 9-1-1 immediately.Electrical Burning Odors
Although loose or faulty electrical connections in your heating and cooling systems can cause wires to overheat and emit an electrical burning odor, these types of smells are more often the result of failures in the HVAC system’s working parts. If a bearing in the motor seizes up, for example, the equipment may overheat and begin to melt the motor windings. Even a clogged air filter can force the motor to overheat. If changing the filter doesn’t resolve the problem, schedule professional service before the entire system is compromised.Oil Odors
Oil odors emanating from oil-burning furnaces and boilers are typically accompanied by a telltale oil leak in a burner, pipe or tank. Some leaks can be easily resolved by tightening a fitting. If you smell oil but see no signs of a leak, enlist help from a technician at The Cooling Company to identify the source. The cause may be anything from a plugged oil nozzle to a blocked flue or chimney.Damp or Moldy Smells
Air conditioners remove water vapor as well as heat from the air, but when humidity levels are too high or if the unit itself is too small, you may notice a musty smell or muggy feeling in the air. A persistent musty and damp odor can also be a sign of an undetected leak in the equipment or in your plumbing system. Leaky ductwork allows moisture penetration as well, and damp air ducts are the perfect breeding ground for mold and mildew. The Cooling Company offers a broad array of services and products that can improve your indoor air quality and enhance your comfort. Whether you need a tune-up to ensure your heater is operating safely in time for the winter season, or a new AC system to manage indoor humidity levels, you can count on the experts at The Cooling Company for fast and effective solutions. Call us at (702) 567-0707.How to Tell a Natural Gas Leak from Other “Rotten Egg” Smells - and What to Do First
Natural gas is odorless; utility companies add a sulfur-like “rotten egg” scent (mercaptan) so people can detect leaks. That same smell, however, can sometimes come from other sources - sewer gas, a dead animal in a wall or attic, or a stuck pilot light. Telling them apart quickly helps you take the right safety steps.Quick Checklist (First 5 Minutes)
- Don’t flip light switches or use electronics - a spark can ignite gas.
- Open doors and windows to ventilate if it’s safe to do so.
- If the smell is strong or you suspect a leak, evacuate everyone (including pets) and call 9-1-1 right away.
- From a safe location, call your gas utility (Southwest Gas serves much of the Las Vegas Valley) or emergency services.
- If the odor is faint and localized (near a drain or garbage), it may be sewer gas - still address promptly.
Smell Pattern and Location
- A continuous strong sulfur smell inside near a furnace, water heater, clothes dryer, or kitchen range often points to a gas appliance.
- If the odor is strongest near floor drains, toilets, or vents, suspect sewer gas or a dried trap.
- If you can’t localize it, treat it as a potential gas leak and evacuate.
Local Context: Las Vegas Neighborhoods
In older North Las Vegas and central Las Vegas homes with aging plumbing and vents, sewer gas issues are more common. In fast-growing neighborhoods like Summerlin and Henderson, new construction issues (improper venting or capped pipes) can cause odors. Our licensed, NATE-certified technicians at The Cooling Company serve all these areas and can inspect gas lines and appliances safely.When to Call The Cooling Company
If a pilot light is out and the smell disappears after ventilating, you can follow the appliance manufacturer’s relight instructions - but if you ever feel uncertain, call our emergency team. We respond to odor calls and perform safe appliance checks, leak inspections, and coordination with your gas utility.Immediate Safety Steps and Simple Checks for Electrical or “Burning” Smells
An electrical burning smell coming from an HVAC system can mean overheated wiring, a failing motor, or a shorted component. Quick, safe actions can prevent fire or further equipment damage.Immediate Actions
- Turn off the system at the thermostat and at the breaker panel. Do not try to “reset” a breaker repeatedly.
- If you smell burning near the air handler or furnace, keep people and pets clear of the area and call a professional.
- Avoid touching wiring or attempting repairs yourself. Even a small mistake can be dangerous.
Safe Do-It-Yourself Checks
- Check and replace a dirty air filter - clogged filters are a common cause of motor strain and overheating. (Replace filters every 1–3 months, more often in dusty Las Vegas neighborhoods.)
- Look for visible signs of smoke, melted insulation, or scorch marks around the air handler access panel - if present, leave the system off and call a pro.
- Note any tripped breakers or blown fuses and which circuit they’re on; this helps technicians diagnose the problem faster.
Why Professional Diagnosis Matters
Technicians use proper testing tools to find overloaded circuits, bad capacitors, seized bearings, or failing motors. Our licensed technicians have experience diagnosing electrical faults in heat pumps and furnaces across Henderson, North Las Vegas, and the valley - and we coordinate electrical repairs safely with licensed electricians when needed.Practical Homeowner Tip
If a smell appears only during startup after a long idle period, it could be dust burning off - run the fan for 10–15 minutes on a cool setting to clear it. If the smell returns, stop using the system and call us. For an estimate on service rates and labor, see our guide to HVAC Labour Rates.Preventing Mold and Controlling Humidity in Las Vegas Homes
While Las Vegas is mostly dry, AC systems run nearly year-round and monsoon season brings higher humidity. That combination - plus hot attics - can create moisture problems in equipment and ducts. Here are practical steps to reduce damp, musty smells and prevent mold.Homeowner Prevention Checklist
- Replace or clean HVAC filters every 1–3 months. Use pleated filters with MERV 8–11 for a good balance of airflow and filtration.
- Inspect and clean the condensate drain and drip pan once a year. Algae and debris can clog the line; a clogged pan often causes musty odors. A cup of diluted household bleach (or a commercially recommended treatment) can clear organic growth - only when the system is off and the manufacturer allows it.
- Consider a whole-house dehumidifier for homes near water features or during monsoon months. Lowering indoor relative humidity to 40–50% reduces mold growth and improves comfort.
- Seal and insulate ducts in hot attics. Leaky or uninsulated ducts invite hot, humid air that condenses and fosters mold.