Why Your AC Smells Like Rotten Eggs or Sulfur

If your air conditioner starts producing a strong rotten egg or sulfur-like smell, it’s a clear sign that something’s not right. While an air conditioner’s job is to cool and clean your air, foul odors are often a warning of mechanical issues, health hazards, or even safety risks. At Lakeshore Heating & Cooling, we help homeowners in Eastlake and surrounding areas identify and fix these issues quickly and safely.

Common causes of rotten egg or sulfur smells from your AC

If your air conditioner starts to smell like rotten eggs or sulfur, it’s more than just an unpleasant odor—it’s often a warning sign that something serious is happening inside your HVAC system or somewhere nearby. At Lakeshore Heating & Cooling, we’ve helped many homeowners throughout Eastlake and the surrounding areas track down and resolve these alarming smells quickly and safely. Below are the most common causes of this odor and what they might mean for your home.

1. Natural gas leak near the HVAC system

While your air conditioner itself doesn’t run on natural gas, a rotten egg or sulfur smell could be caused by a nearby gas leak. Natural gas is naturally odorless, but utility companies add a chemical called mercaptan to give it a distinct, sulfur-like smell for safety.

• • • If you notice the odor suddenly and strongly, it could indicate a serious leak near your HVAC equipment or gas appliances.
    • Gas leaks are a major safety hazard. You should immediately turn off your HVAC system, evacuate your home, and contact your gas company or emergency services.
    • Do not use your thermostat, flip switches, or attempt to diagnose the issue yourself.

If you've ruled out a gas leak but the smell persists around your HVAC system, it's time to call Lakeshore Heating & Cooling for professional air conditioning repair and inspection.

2. Dead animal in the ductwork or air handler

Unfortunately, pests and small animals sometimes find their way into ductwork or outdoor condenser units. If they become trapped and die, the decomposition process can emit a strong, foul odor that travels through your ventilation system.

• • • The smell may be strongest in one area, especially if the animal is trapped near a specific vent or return.
    • You may also notice unusual airflow or signs of pest activity.

Our team can perform a full duct inspection and cleaning service, removing the source of the smell and helping to seal access points to prevent future infestations. This is a common service request for homeowners across Willoughby, Mentor, and other parts of Lake County.

3. Sewer gas entering the HVAC system

Another possible cause is sewer gas. If there’s a plumbing issue nearby—such as a dry trap, blocked vent stack, or leaking drain line—sewer gases may enter your home and get pulled into the return ducts of your HVAC system.

• • • This often happens in basements or utility rooms, especially if floor drains aren’t used regularly.
    • If the smell stays even when the system is off, the problem may lie in the surrounding environment, not inside the system itself.

While this may not be a direct failure of your HVAC system, our technicians can help determine if your air handler or return ductwork is drawing in air from problem areas and recommend solutions, such as zoning, sealing, or rerouting.

4. Electrical failure or overheating component

In some cases, the sulfur-like smell may not be from gas or animals at all—it may be coming from overheated electrical components within your HVAC system. Capacitors, wiring, motors, and control boards can overheat and give off a burning or sulfurous odor.

• • • This is often accompanied by buzzing noises, tripped breakers, or system malfunctions.
    • If you notice any combination of smell and odd electrical behavior, shut off your system immediately.

We offer emergency HVAC repair services throughout Wickliffe, Willoughby Hills, and Mentor-On-The-Lake, and can safely diagnose and replace any failing components before they create a fire risk.

Why it’s important to act fast

An AC system that smells like rotten eggs or sulfur is never normal—and it should never be ignored. Acting quickly could prevent:

• • Health risks from gas leaks, pest-borne bacteria, or mold
  • Electrical hazards, including potential fire
  • Major system failures that are more expensive to fix later

At Lakeshore Heating & Cooling, we take these situations seriously. Our licensed technicians perform thorough system diagnostics, identify the source of the problem, and offer effective, long-lasting solutions. Whether you need AC repair, duct cleaning, or full system replacement, we’ll ensure your home stays safe and comfortable.

How to prevent bad AC smells

Once the immediate issue is resolved, it’s important to take preventive steps to avoid unpleasant AC odors in the future. These smells are often tied to neglect, pest entry, or poor airflow—all of which can be minimized with a few key habits:

• • Schedule routine HVAC maintenance at least once a year, ideally before each cooling season, to catch developing issues early
  • Change your air filters regularly, typically every 1–3 months depending on usage, pets, and allergies
  • Inspect and seal your ductwork to prevent small animals, dust, or moisture from entering and accumulating
  • Keep nearby gas appliances and utility lines properly maintained, especially if they’re located near your air handler or duct returns
  • Watch for water buildup near condensate drains or coils, which can create mold or mildew smells if left untreated

Our preventative maintenance plans include detailed inspections, filter checks, and cleaning services that can catch and correct many odor-causing problems before they impact your comfort—or your health. If you’re in Eastlake or surrounding areas, we make it easy to stay ahead of HVAC issues year-round.

.Why choose Lakeshore Heating & Cooling?

We’ve built a reputation in Eastlake and across Lake County for honest, dependable HVAC service. Homeowners choose us because we offer:

• • Licensed, experienced technicians
  • Transparent pricing with no surprises
  • On-time service and respectful customer care
  • Solutions that last—not just temporary fixes

Whether you need a small repair or a full system upgrade, we’re ready to help you breathe easier.

Proudly serving Lake County and surrounding areas

Lakeshore Heating & Cooling provides expert air conditioning and heating services in:

• • Eastlake
  • Willowick
  • Willoughby
  • Willoughby Hills
  • Wickliffe
  • Mentor
  • Mentor-On-The-Lake
  • Fairport Harbor
  • Painesville
  • Perry
  • Grand River
  • Painesville Township

Call today for safe, professional AC repair

If your air conditioner smells like sulfur or rotten eggs, don’t ignore it. Call Lakeshore Heating & Cooling today for fast, professional service. We’ll find the cause, fix the issue, and get your home back to feeling fresh and comfortable.

Request an estimate or call now—serving Eastlake, Ohio and all nearby areas with reliable, trusted HVAC solutions.