Smoke Coming From Vents When AC Is On: What To Do

Smoke Coming From Vents When AC Is On

You’re slumped on the couch enjoying your favorite TV show until the smoke blowing from your AC suddenly catches your eye. Engulfed by a wave of panic, you turn it off in a heartbeat. Before you entertain the thought of shelling out hundreds of bucks for a new unit, a quick Google search of ‘smoke coming from vents when ac is on’ brings you to this guide.

When you see smoke coming from vents when AC is on, you want to know if it’s a normal occurrence or an indicator of a bigger problem. Well, you’ve come to the right place. Here we will share how to determine the cause of the smoke and what you can do to remedy the situation.

Read on as we dive into the steps to follow when you’re in this predicament and show you what to do when your AC is blowing smoke.

Why Is Your AC Blowing Smoke?

Why Is Your AC Blowing Smoke

Let’s delve into a few common reasons.

1. A Clogged Drain Hole

If your AC is an older model blowing odorless white smoke, a clogged drain hole is likely the culprit. Condensation is a normal phenomenon with all AC units. Newer models collect dew points in a pan and reuse them to prevent overheating and cool the components.

Older units have drain holes that serve as escape points for the water. If the hole gets clogged, the water remains trapped in your AC. When the water droplets come into contact with the heat in your AC, it becomes the steam you see pouring out of the unit.

Although this is one of the more benign kinds of air conditioner smoke, you’ll want to have the clog removed by an expert. Additionally, consider upgrading to a newer model that utilizes condensation.

2. Humidity

If the internal humidity of your AC is lower than that of the air around the air vent, there’s a chance you’ll notice a small amount of fog known as dew points. Keep in mind that the fog is odorless and doesn’t leave your unit susceptible to damage.

Although there’s the option, you don’t need to rope in a professional to handle the humidity. Instead, allow the unit to run on ‘high’ for several minutes. Doing so helps to achieve the equilibrium between the humidity in the atmosphere and that of your AC. If the humidity issue keeps recurring, that might be your cue to examine your filter.

If it’s clogged, it can exasperate the situation and cause vapor to spew out of your air conditioner regardless of the duration that the unit has been running. We recommend having a professional check your filter every two to three months.

3. Overheating

If your AC is blowing smoke that is accompanied by an odor, there’s a chance you have a bigger problem that goes beyond mere condensation. It’s a no-brainer that an AC comprises electrical parts. Therefore, without adequate ventilation, these components will overheat, generating a burning smell. If ignored, you’ll notice dark smoke and a pungent smell stemming from your AC that might be accompanied by noise.

Overheating is typically a problem that arises from adversely clogged air filters that restrict proper ventilation of the unit’s parts. Upon noticing this issue, shut off the air conditioner and call a professional. They’ll likely replace the air filter coupled with the component that is generating smoke.

4. A Direct Component Problem

Your AC might be properly ventilated but still producing a pungent burning smell coupled with smoke. If it’s an older model, there’s a high likelihood that one of the components has succumbed to wear and is generating smoke.

The typical culprits are the fan motor and the fan belt for a belt-driven fan. Besides a terrible smell, this type of air conditioning smoke can be detrimental to your health when inhaled. It’s also harmful to the environment.

If you’re in this predicament, turn off the AC immediately and contact an HVAC system expert. Depending on the root cause of the smoke, an expert may suggest replacing the entire unit.

5. Electrical Failure

Faulty electrical components and wiring can cause a fire hazard that produces a burning smell accompanied by smoke. Leaving the unit operating in this condition can be hazardous, so turn it off, unplug it, and have a professional conduct a thorough assessment.

Is Your AC Setting Off The Smoke Alarm?

Although AC smoke is one thing, setting off smoke alarms is a whole new ballgame. It’s not related to smoke from the unit but rather a feature in the alarm designed to alert a homeowner of a power surge.

If the unit’s electrical setup isn’t well configured, it can trigger a power surge whenever it’s running. When this happens, you should disconnect the air conditioner and call an electrician or the professional who installed the unit. Your AC setting off the smoke alarm is indicative of an electrical wiring issue that needs immediate attention.

How To Prevent Your AC From Blowing Smoke

Let’s explore a few pointers to avoid the issue of a smoking AC altogether.

1. Replace Your Filter Frequently

Altering the filter of your AC is cheap and easy. Besides preventing smoke, it will boost the quality of air in your home. Although examining and replacing your filter is advisable every three months, keep in mind that it’s nothing more than a guideline.

Therefore, we encourage you to check the filter more regularly if you reside in an area with poor air quality. It’s not difficult to notice when an air filter is dirty, in which case you’ll need to keep your eyes peeled and change the filter even though it seems too soon. You want to avoid dirt buildup on the filter.  

2. Annual or Bi-Annual Checkups

Find a local HVAC system expert you trust to perform your AC unit’s bi-annual or annual checkup. For older models, a checkup every three months might be necessary to avoid unwarranted surprises. The checkups will unveil issues that may become serious down the line. It’s always better to handle these issues before your AC starts billowing smoke on a random Saturday afternoon.

3. Invest In a Properly Sized AC

Ensure your HVAC system expert has installed the right sized AC for your home to save you from a wealth of other problems such as humidity and overheating.


Although white, odorless smoke isn’t a cause for alarm, especially if it’s faint and you reside in a high humidity area, thick, dark smoke billowing from your AC is a hazardous problem that calls for professional help.

Lastly, keep in mind that prevention is always better than cure. Therefore, by taking care of your AC through frequent checkups and component replacements, it will reward you by remaining in tiptop condition for years down the road. The predicament of ‘smoke coming from vents when ac is on’ will be the least of your concerns.

Frequently Asked Questions

What is the sound of a bad AC compressor?

You’ll notice the sound of a grinding or high-pitched noise if you have a bad AC compressor. Additionally, it might be accompanied by smoke and a burning smell.

Should you be alarmed when you see air coming out of your AC?

Seeing air blowing from your AC is condensation. It occurs when cool air from your unit meets the warm air in your home’s atmosphere. Therefore, it’s not a cause for alarm.

Which components are likely to be the culprits of smoke blowing from your AC?

The first culprit is the fan belt that consists of rubber and helps the fan blades spin for air circulation. When it malfunctions or is overworked, it overheats, producing a pungent burning, rubbery smell. The second culprit is the fan or blower motor that eventually gets weak and has to work harder to get the job done, causing overheating, and producing smoke and that electrical smell.