10 Unpleasant Air Conditioner Smells and How to Fix Them | AC Guide

When your air conditioner switches on and an unexpected smell hits you, it can ruin your comfort instantly. Some AC smells are harmless… others can signal gas leaks, electrical hazards, mould growth or dangerous refrigerant exposure.

This guide breaks down the 10 most common air conditioner smells, what causes each one, how to fix them and when to call a professional. Perfect for Gold Coast homeowners who want clean, safe, fresh air all year round.

1. Rotten Eggs Smell

Cause:

A strong sulfur smell is often linked to a natural gas leak entering your ductwork. This is a serious safety issue, not an AC fault.

Fix:

• Turn off the gas if safe.

• Evacuate everyone.

• Call emergency services or a licensed technician immediately.

2. Dirty Socks Smell

Cause:

The classic “dirty sock syndrome” happens when stagnant water, bacteria and moisture build up on evaporator coils.

Fix:

• Replace the air filter.

• Book a coil deep clean + drain flush.

• Prevent with yearly servicing.

3. Mould & Mildew Smell

Cause:

Humidity on the Gold Coast makes mould grow quickly inside AC units, ducts and drip trays.

Fix:

• Start with a filter change.

• If smell stays, book a duct clean + mould treatment.

• Keep humidity low inside your home.

4. Burning or Gunpowder Smell

Cause:

A burning smell can indicate overheating wires, fan motor issues or electrical failure.

Fix:

• Turn off the AC immediately.

• If the smell intensifies, leave the house and call the fire department.

• Book electrical diagnosis and repair.

5. Exhaust Fumes

Cause:

AC systems do not create exhaust fumes — smells like this often come from a motor malfunction or refrigerant leak.

Fix:

• Turn off the system.

• Book an urgent repair.

6. Sweet Chemical / Coolant Smell

Cause:

A sweet, chemical or “car coolant” smell may indicate refrigerant leakage, often Freon or R-410A.

Fix:

• Turn off system & ventilate the area.

• Call a professional — refrigerant handling is licensed work only.

7. Cigarette Smoke Smell

Cause:

If anyone has smoked indoors, residue gets trapped in filters, coils and ductwork and is recirculated.

Fix:

• Replace filters monthly.

• Schedule yearly coil & duct cleaning.

• Use an indoor air purifier.

8. Skunk or Sulfur Spray Smell

Cause:

A skunk-like sulphur smell often means a small animal sprayed near or inside the outdoor unit.

Fix:

• Turn off AC.

• Air out the home.

• Book inspection & outdoor unit cleaning.

9. Garbage or Dead Animal Smell

Cause:

A rotting garbage smell usually means a dead rodent or bird inside the ducts or the outdoor unit.

Fix:

• Stop running the AC.

• Call for a full duct clean & inspection.

• Seal off any access points.

10. Damp, Musty, "Wet Dog" Smell

Cause:

Usually caused by:

• Clogged drain line

• Dirty indoor fan

• Wet filters

• High humidity from recent storms

• Bacteria build-up on coils

Fix:

• Clean or replace your filter.

• Get the fan barrel professionally cleaned.

• Request a drain flush.

• Use a dehumidifier in wet months.

How a Professional Hydro Clean Fixes These Smells

A hydro clean goes far deeper than a standard service. Using high-pressure water, safe detergents and specialist tools, technicians remove:

• Mould hidden inside the evaporator

• Bacteria causing “dirty sock” or musty smells

• Dust trapped in the fan barrel

• Slime and blockages in the drain line

• Odour-causing residue inside the casing

• Allergens, pet dander and bacteria

This restores fresh, cool, efficient airflow — especially important in the humid Gold Coast climate.

Q&A - Common AC Smell Questions

Q: Why does my AC smell worse at night?

Humidity rises at night on the Gold Coast, which activates mould spores and magnifies odours.

Q: Can AC smells make you sick?

Yes. Gas leaks, refrigerant leaks, mould and electrical faults can be hazardous.

Q: How often should I service my AC to avoid smells?

Every 12 months or every 6 months if you live near the beach, have pets or run the AC daily.

Q: How do I know if the smell is dangerous?

If it smells like gas, chemicals, burning or exhaust, turn the system off immediately.

Need your AC to smell fresh again?

EvidiAir specialises in deep cleaning, repairs and diagnostics for all split-system and ducted brands across the Gold Coast.

✔ Expert technicians

✔ Same-day service available

✔ Hydro clean for maximum freshness

✔ Safe, family-friendly cleaning products

📞 Call EvidiAir now on 041475300 or book online for fast professional AC service.