# Why does my air conditioner smell musty or like dirty socks? 1. [Home](https://arlite.co/) 2. [Support](https://arlite.co/support/) 3. [Air conditioning](https://arlite.co/support/air-conditioning/) 4. Why does my air conditioner smell musty or like dirty socks? **Browse support** [Support home](https://arlite.co/support/) [Solar](https://arlite.co/support/solar/)[View all](https://arlite.co/support/solar/) - [How does a solar power system work in a Brisbane home?](https://arlite.co/support/solar/how-does-a-solar-power-system-work-in-a-brisbane-home/) - [How do I turn off a solar inverter safely?](https://arlite.co/support/solar/turn-off-solar-inverter-safely/) - [Do solar panels work during a blackout?](https://arlite.co/support/solar/solar-during-power-outage/) - [Can I add a battery to my existing solar system?](https://arlite.co/support/solar/add-battery-to-existing-solar-system/) - [Hail or storm damage to solar panels: what to do](https://arlite.co/support/solar/hail-storm-damaged-solar-panels-what-to-do/) [Air conditioning](https://arlite.co/support/air-conditioning/)[View all](https://arlite.co/support/air-conditioning/) - [Why does my air conditioner smell musty or like dirty socks?](https://arlite.co/support/air-conditioning/air-conditioner-smells-musty-dirty-socks/) - [Why is my air conditioner not cooling or heating properly?](https://arlite.co/support/air-conditioning/air-conditioner-not-cooling-or-heating/) - [Why is my air conditioner leaking water inside?](https://arlite.co/support/air-conditioning/air-conditioner-leaking-water-inside/) - [Can solar panels run my air conditioner at night?](https://arlite.co/support/air-conditioning/can-solar-panels-run-my-air-conditioner/) - [What should I ask before getting an air conditioner installed?](https://arlite.co/support/air-conditioning/questions-to-ask-before-air-conditioner-installation/) [Electrical](https://arlite.co/support/electrical/)[View all](https://arlite.co/support/electrical/) - [Why does my circuit breaker keep tripping?](https://arlite.co/support/electrical/circuit-breaker-keeps-tripping/) - [Why does my safety switch keep tripping?](https://arlite.co/support/electrical/safety-switch-keeps-tripping/) - [Burning smell or hot power point: what to do right now](https://arlite.co/support/electrical/burning-smell-hot-power-point/) - [Why is there no hot water? Electrical faults explained](https://arlite.co/support/electrical/no-hot-water-electrical-checks/) - [What smoke alarms does Queensland require?](https://arlite.co/support/electrical/queensland-smoke-alarm-requirements/) [Costs and finance](https://arlite.co/support/costs-and-finance/)[View all](https://arlite.co/support/costs-and-finance/) - [How does interest-free finance work for home energy upgrades?](https://arlite.co/support/costs-and-finance/interest-free-finance-home-energy-upgrades/) - [What affects the cost of a home battery in Brisbane?](https://arlite.co/support/costs-and-finance/what-affects-home-battery-cost-brisbane/) - [Can I get compensation for a power outage in Queensland?](https://arlite.co/support/costs-and-finance/power-outage-compensation-energex/) - [How much does an electrician cost per hour in Brisbane?](https://arlite.co/support/costs-and-finance/electrician-cost-brisbane/) - [What affects switchboard upgrade cost?](https://arlite.co/support/costs-and-finance/switchboard-upgrade-cost/) [Air conditioning](https://arlite.co/support/air-conditioning/) A musty or dirty-sock smell usually means moisture and mould or bacteria are building up inside the unit, which a technician can deal with. By Aaron Midgley, Arlite Energy Last reviewed 30 October 2026 4 minute read **No DIY.** Electrical work must be done by a licensed electrician. Never open, repair, test or modify electrical equipment yourself, even if it looks simple. This guide explains what is happening; it is not a how-to. **On this page** 1. Why do air conditioners get smelly? 2. Are all smells the same? 3. Is a musty smell harmful? 4. Why does the smell come back? 5. Can sprays or home remedies fix it? 6. How can I reduce the chance of smells? 7. What to note before you call 8. What does a servicing visit involve? 9. Frequently asked questions A musty or dirty-sock smell from an air conditioner usually means moisture, dust and mould or bacteria have built up on the cold parts inside the indoor unit or its drain. It is common in humid Brisbane summers. Stop using the unit if the smell is strong and have it inspected and serviced by a licensed technician. ## Why do air conditioners get smelly? When an air conditioner cools the air, moisture collects on the indoor coil and is meant to drain away. If the coil stays damp and dust builds up, mould and bacteria can grow, and the fan then blows that smell into the room. Trade websites often call this “dirty sock syndrome” because of the sour smell. It is more common in damp climates and when a unit is used often for short periods. ## Are all smells the same? No. Different smells point to different causes: - **Musty or sour, like damp socks:** mould or bacteria on the coil or in the drain tray. - **Rotten egg or sewer-like:** can come from a drain problem and is worth reporting to a technician. - **Burning or hot plastic:** an electrical or motor problem. This is a safety issue, not a cleaning issue. - **Chemical or oily:** could involve a refrigerant leak or something else, and needs a licensed technician. ## Is a musty smell harmful? Mould and bacteria can irritate some people, particularly those with asthma, allergies or sensitive airways. A mild smell is usually an annoyance rather than an emergency, but it is worth dealing with, especially in bedrooms or if anyone in the home is unwell. If someone has breathing problems, speak to a doctor as well. Stop using the unit and call if The smell is burning, like hot plastic or electrical, or you see smoke, sparks or feel heat from the unit. Leave the building and call 000 for fire, smoke or sparks. For a musty smell that does not go away, stop using the unit and contact an ARC-licensed air-conditioning technician. ## Why does the smell come back? If the underlying moisture or dust problem is not dealt with, the smell returns. Common reasons are a drain that is not working properly, a unit that is rarely serviced, or a system that is too big for the room so that it keeps starting and stopping and never dries out properly. A technician can look at the whole system rather than only the visible parts. ## Can sprays or home remedies fix it? Sprays and household products can mask a smell without fixing the cause, and putting products into a unit may damage it or create a safety risk. The manufacturer’s maintenance guidance and owner’s manual set out what is suitable for your model. For anything beyond that, rely on a licensed technician. ## How can I reduce the chance of smells? Following the manufacturer’s maintenance guidance and having the unit serviced regularly by a licensed technician helps keep the unit in good condition. Using it normally, rather than leaving it off for months and then switching it on, also helps. Your manual will explain what the maker recommends. ## What to note before you call 1. Describe the smell — Write down whether it is musty, sour, chemical or burning, and whether it is stronger at start-up. 2. Note when and where — Record which rooms and which modes (cooling, heating, fan) are affected. 3. Photograph the labels — Take a photo of the make and model label and any display codes without touching or opening the unit. What you can safely check Look at the unit and the air from a distance, note when the smell appears, and photograph any visible marks or stains on the casing. Read the manual’s maintenance section. Do not open the unit or touch any internal parts. ### What does a servicing visit involve? A licensed technician will inspect the indoor unit, the drain and the condition of the parts that handle air and moisture, and carry out the cleaning that the manufacturer’s guidance allows. They will tell you if anything is worn or faulty and whether the system suits the room. ## Frequently asked questions - It is a trade name for the sour, sweaty-sock smell caused by moisture and microbes building up on the indoor coil of an air conditioner. - The first blast of air carries odours that built up while the unit was idle and damp, so the smell is often strongest at start-up. - Humidity makes it more likely, because moisture is more abundant and takes longer to dry out. - A burning or hot-plastic smell can. Stop using the unit, keep clear, and call 000 if there is smoke, sparks or fire. [Learn about Air Conditioning](https://arlite.co/services/air-conditioning/) Related services: [Ducted Air Conditioning](https://arlite.co/services/air-conditioning/ducted-air-conditioning/) ## Official guidance For the rules and safety information that apply to your home, go to the regulators and industry bodies directly. - [Australian Refrigeration Council](https://www.arctick.org/) - [Energy Rating (Australian Government)](https://www.energyrating.gov.au/) - [Electrical Safety Office Queensland](https://www.electricalsafety.qld.gov.au/) Was this helpful? Written by the team at Arlite Energy, a Brisbane business that designs and installs solar, air conditioning and electrical work for homes and businesses. We write these guides in plain English so you know what is happening in your home. ## Related articles - [Air conditioningWhy is my air conditioner leaking water inside?Water dripping from an indoor unit usually means the condensation drain is blocked or the unit is icing up, and a technician should look at it.](https://arlite.co/support/air-conditioning/air-conditioner-leaking-water-inside/) - [Air conditioningHow often does an air conditioner need servicing?Many manufacturers and installers advise servicing every one to two years, but follow your manual and warranty and use a licensed technician.](https://arlite.co/support/air-conditioning/how-often-air-conditioner-servicing/) - [Air conditioningWhy is my air conditioner not cooling or heating properly?Weak cooling or heating usually comes from airflow, settings, sizing or refrigerant problems, and some of these need a licensed technician.](https://arlite.co/support/air-conditioning/air-conditioner-not-cooling-or-heating/) - [Air conditioningWhy is my air conditioner making a loud or strange noise?Rattling, buzzing, grinding or squealing can mean loose parts, a failing fan or compressor, or an electrical fault, so stop and get it checked.](https://arlite.co/support/air-conditioning/air-conditioner-making-loud-strange-noise/) ## Still stuck? Tell us what is going on and we can arrange a call-out. [Book a call-out](https://arlite.co/contact/) On this page 1. Why do air conditioners get smelly? 2. Are all smells the same? 3. Is a musty smell harmful? 4. Why does the smell come back? 5. Can sprays or home remedies fix it? 6. How can I reduce the chance of smells? 7. What to note before you call 8. What does a servicing visit involve? 9. Frequently asked questions --- **Arlite Energy**, Unit 1, 1468 Anzac Avenue, Kallangur QLD 4503. Phone [(07) 3062 9299](tel:+61730629299), email [info@arlite.co](mailto:info@arlite.co). Monday to Friday, 7am to 5pm. Page: https://arlite.co/support/air-conditioning/air-conditioner-smells-musty-dirty-socks/ Site index for agents: [llms.txt](https://arlite.co/llms.txt), [sitemap](https://arlite.co/wp-sitemap.xml), [developer resources](https://arlite.co/developers/).