December 22, 2025

When cold mornings finally roll into East Arkansas, most homeowners switch their heating system on for the first time in months. And almost instantly, many notice it… a strange smell. Sometimes it’s dusty. Sometimes it’s musty. Sometimes it’s strong enough to make you wonder if something’s burning.

If you’ve been there, you’re not alone.
 

At Mohr Air Conditioning, heater smells are one of the most common questions we get in early winter. The good news is that some odors are completely normal. But others can be a sign that something in your system needs attention—fast.

Here’s what those smells really mean, when they’re harmless, and when it’s time to call in a Mohr technician.

 

1. Dusty or Burning Smell (Usually Normal)

What it smells like:
 Burning dust, burning hair, “hot” smell from metal parts heating up.

What’s causing it:
 During Arkansas’s long, humid summers, your furnace or heat pump rarely runs. Dust naturally settles on the heating elements, heat exchanger, and internal components.
 When you turn the heater on for the first time, that dust burns off.

How long should it last:
 Anywhere from a few minutes to an hour.

When it becomes a problem:

• The smell lasts for several hours
   
• Your heater smokes or sets off alarms
   
• You haven’t had a tune-up in over a year
   

If the smell persists longer than expected, it’s smart to have your system checked to make sure nothing is overheating.

2. Musty or Mildew Odor

What it smells like:
 “Dirty socks,” damp basement odor, or a wet/dusty smell.

Likely causes:
East Arkansas humidity can lead to moisture building up in your HVAC system—especially if you’re using a heat pump.

You may be dealing with:

• Mold or mildew inside the system
   
• A dirty or clogged air filter
   
• Condensate drain issues
   
• Moisture in the ductwork
   

What to try first:
 Change your air filter.
 If the smell doesn’t go away, schedule a cleaning or duct inspection to prevent allergens from circulating through your home.

3. Electrical or Burning Plastic Smell (Not Normal)

What it smells like:
 Hot wires, melting plastic, or an overheated electrical component.

This can indicate serious issues such as:

• A failing blower motor
   
• Overheated wiring
   
• Motor bearings going bad
   
• Cracked heat exchanger
   
• Shorted capacitor
   
• Loose electrical connections
   

What to do:
 Turn the system OFF immediately and call Mohr Air Conditioning. Electrical smells are not something to ignore—continuing to run the system could create a fire hazard.

 

4. Rotten Egg or Sulfur Smell (Emergency)

If your heater smells like rotten eggs, leave the home immediately and call your gas company.
 The “rotten egg” odor is added to natural gas as a safety signal for leaks.

Do NOT:

• Use appliances
   
• Turn lights on or off
   
• Try relighting anything
   
• Stay indoors
   

Once the gas company gives the all-clear, our technicians can safely inspect and repair your furnace.

5. Smoky or Burnt Odor From Vents

What it smells like:
 Smoke, soot, or burnt dust on metal.

This can happen when:

• A component in the furnace overheats
   
• The air filter is extremely clogged
   
• Dust buildup inside the unit ignites
   
• Heat strips in a heat pump are malfunctioning
   

Restricted airflow can cause your system to work harder, overheat, and fail—especially in homes outside town where filters get dirtier faster.

What to do:
Turn off the heater and schedule service before running it again.

How to Prevent Heater Odors in the FutureChange Your Air Filter Regularly

Every 30–60 days (more often if you have pets or dusty conditions).

Get a Fall Tune-Up

Mohr’s tune-up includes cleaning, testing, inspecting, and making sure your system is safe before winter arrives.

Keep the Area Around the Furnace Clear

This prevents dust buildup and fire risks.

Have Your Ducts Checked

Especially if your home feels musty or has ongoing indoor air quality problems.

 

When to Call Mohr Air Conditioning

Reach out to our team if:

• The smell lasts more than an hour
   
• You notice a burning, electrical, or chemical odor
   
• Your heater is blowing cold air
   
• The system is making new or loud noises
   
• Your smoke detector or CO detector goes off
   
• You haven’t had a system inspection this year
   

You shouldn’t have to guess whether your heater is safe. Our technicians can diagnose the issue, clean your system, and make sure your home stays warm and comfortable all winter.

Stay Warm, Safe, and Comfortable This Winter

If your heater smells strange or you’re just not sure whether a smell is harmless, Mohr Air Conditioning is here to help. From tune-ups to repairs to seasonal maintenance, we’ll make sure your system is running safely and efficiently before the real cold hits.