How to Remove Musty Smells from Your Portable AC

Written by: Paul Cathro

Updated on: December 23, 2022

Man fixing a portable air conditioner

Portable air conditioners are excellent at cooling individual rooms and small to medium-sized living spaces.

Still, the small air filters collect dust, dirt, and dander, which can create musty smells if left unchecked. 

Mustiness is especially common in areas with high humidity because moisture in the air traps odors in the air filter, like grease to an extraction fan.

Evaporator coils, condensate tanks, and drain lines can also produce musty smells. 

The good news is that removing musty smells from your portable AC isn’t tricky nor particularly nasty.

You’ll need to get your hands dirty and invest in a few cleaning products, but it’s plain sailing when you know what to do.  

Here’s everything you need to know about removing musty smells from your portable AC:

What Causes Odors in a Portable AC?

While odors generally can be organic or inorganic in origin, in the case of musty smells in portable AC, the offenders are always organic. 

Odors in portable AC are produced by bacteria – living organisms that feed on compounds and convert them into gaseous, volatile waste. 

When bins stink, armpits smell and portable AC is musty, bacteria are to blame as they feed on moisture and compounds. 

This can manifest as mold in filters, tanks, and drain lines. Depending on the bacteria and environment, mold can be fuzzy, furry, or slimy. Bacteria thrive in humid, wet environments, and a portable AC provides the ideal breeding ground. 

Mold is dangerous because it can cause an allergic reaction and asthma attacks, and some people are susceptible to mold spores. 

If your portable air conditioner hasn’t had a thorough cleaning for a few months, it’s time to don those gloves and get started.

Musty smells worsen unchecked, and you will improve the cooling efficiency of your portable AC with clean components.  

How to Fix a Portable Air Conditioner That Smells Musty

Firstly, unplug your portable AC and place it on a solid, level surface. 

To eliminate musty smells, you must clean the air filter, evaporator coil, condensate tank, and drain line. 

Refer to your portable AC user manual and disassemble the unit, using only gentle force when releasing parts held together with clips. 

You may need a small screwdriver to access specific components – a Phillips or Pozidriv screwdriver will do the job. 

You should wear disposable nitrile or latex gloves when cleaning your portable AC, and it’s also a good idea to wear safety glasses. 

Breathing apparatus is recommended when handling chemicals like ammonia, and you should wear a face mask if there’s a risk of airborne mold spores. 

1. Clean the Air Filter

Your portable air conditioner probably has a removable air filter – although not all of them are cleanable (your user manual will tell you). 

If the air filter is cleanable:

  • Take the filter outside and blow as much dust and debris off the filter using a canister of compressed air. 
  • Take a vacuum cleaner and remove as much lint and dust as possible but be careful not to damage the filter. 
  • Submerge the filter in mild soapy water and use a soft-bristled brush to scrub it clean – washing up liquid is best. 
  • Spray the filter with an antibacterial cleanser. 
  • Let the filter dry thoroughly before putting it back.

If the air filter is not cleanable, you should buy a replacement. But don't worry they're relatively inexpensive. Just make sure to get the right fit for your model.

2. Clean the Evaporator Coil

Evaporator coils are easy to clean with a non-rinse degreasing agent and a stiff-bristled brush.  

Here’s how to clean the evaporator coil:

  • Open the portable AC casing to expose the coil. 
  • Spray the coil with a non-rinse degreasing cleaning spray or soap-free detergent. 
  • Let the detergent sit for ten minutes. 
  • Respray the coil. 
  • Take a stiff-bristled brush and agitate the coils, wiping in a vertical and horizontal motion to free dirt and grime. 

When you turn your portable AC on, the non-rinse degreasing agent and grime from the coil will flow into the drainage tank with condensation. 

3. Clean the Condensate Tank or Drain Pan

Cleaning the drainage pan is a piece of cake – remove it, rinse it, and scrub it down with an antibacterial washing-up liquid or cleaning spray. 

However, never use an abrasive sponge or scouring pad – these will etch the tank surface and harbor bacterial growth. A soft sponge, microfiber cloth, or mitt is best to wipe the tank down without scratching.

If the tank is discolored and stained, make a mixture of one cup of ammonia with one gallon of water. Submerge the tank in the liquid for 20 minutes and agitate the stain with a soft brush – this should remove mold and stains. 

Always wear gloves and safety glasses/goggles when handling chemicals! If you have breathing problems, you should also wear breathing apparatus, such as a face mask with a P100 cartridge/filter. 

4. Clean the Condensate Drain Line

Condensate drain lines are a massive breeding ground for bacteria, and although not a leading cause of musty smells, they need cleaning to ensure good system performance. 

The best way to clean a thin condensate drain line is to remove the line from the portable AC unit and pump distilled vinegar through it at pressure. 

To generate pressure, you can use a canister of compressed air – fill the drain line with vinegar, hold it at the bottom to keep the vinegar in, and insert the canister at the other end to push the vinegar through at pressure. 

With a thicker drain line, you can usually get a thin pipe cleaner into it, removing mold and physical blockages. 

How Do You Prevent Odors in Your AC System?

The trouble is that many people don’t clean their portable AC until it starts smelling musty, at which point the bacteria are having a party. 

It is easier to control musty portable AC smells with regular cleaning and disinfection so that bacteria cannot take hold and dominate the system.

Our advice is simple – clean your portable AC once per month so that bacteria have no opportunity to thrive. 

Using antibacterial products will also help stop bacteria from growing to keep your portable AC odor and mold-free. 

If you notice musty smells coming from your portable air conditioner, inspect the air filter, evaporator coil, tank, and drain lines.

It is a mistake to clean only the air filter when bacteria happily multiply in tanks and drain lines. 

It would also be prudent to clean your portable AC more frequently if you live in a humid climate.

People living places like Florida should clean their portable AC twice as regularly as those in arid states like Nevada and Montana. 

If you are in a humid climate, it’s also worth considering portable AC with a HEPA filter, which removes dust, pollen, mold, and airborne particles with a size of 0.3 microns. These still need cleaning but offer superior air purification. 

Lastly, if your portable AC is over ten years old, those musty smells might be impossible to spray and brush away.

Upgrading to a newer unit will unlock greater efficiency, and you can pick up some fantastic units for under $400.

About the Author Paul Cathro

Paul is an ex-HVAC engineer with 5 years 'in the trade'.

He acquired in 2022 and aims to make it the internet's most comprehensive HVAC resource for small homes in the next few years.

You can learn more about Paul's story here.

Browse his published work on the website here.

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