Can Mini Splits Produce Carbon Monoxide?

It’s a good thing you’ve asked this question because it shows your concern for your safety and the safety of those you care about, which is everyone I hope. That “Happily Ever After” sign that you can see above has some significance.

I can’t conceive of any possible way that a mini split could produce carbon monoxide. Carbon monoxide is mostly created by systems that burn fossil fuels. Since mini splits are all electric they cannot produce Carbon Monoxide under normal operation.

Fossil fuels, which mainly consist of coal, oil, natural gas, and propane, exist because they were formed from the buried remains of plants and animals that lived millions of years ago. But what about abnormal operation, lets say if a motor or electrical wires short out and burn? I explain more about that as you read.

In addition to what I’ve explained so far, mini splits have no connection to outside air. There are many counties that have adopted new codes that require a certain percentage of outside air to be brought into a home through a duct connected to the return duct of an HVAC system. It’s sometimes referred to as makeup air or a fresh air duct.

Full forced air ducted systems have the room to connect duct work and in addition add a fresh air duct. Mobile homes have that as a requirement and it’s accomplished by adding a small ceiling fan near a central location of the home that goes on and off with the furnace fan.

Maybe you have a mini split or two and you have one of these outside air ceiling fans for fresh air. Have you thought about the possibility of your neighbor exhausting their fossil burning equipment and your fresh air vent sucking it into your home.

I’m not creating fear, just something to be aware of with smaller yards and neighbors just five feet away.

The fresh air duct is supposed to bring in outside air to keep the occupants of the home from breathing the off-gassing that is going on and created by new furniture and the building materials.

You cannot connect an outside air duct to a mini split head. There is just no room on the unit to connect an outside air duct. That’s why mini splits have an alternative name, “ductless”.

Can Mini Splits Emit Harmful Gases?

The only gases related to a mini split would be the refrigerant (Freon) contained in the sealed system. The sealed system refers to those parts of the mini split that are under pressure like the piping, compressor, and coils that the air blows through.

Mini splits hold a relatively small amount of refrigerant compared to a full sized AC unit or heat pump. If your mini split were to for some reason begin to leak refrigerant it’s unlikely to be very hazardous. And with most of the sealed system being outside the likelihood of the leak being inside is very small.

Refrigerant has very little odor. I wrote a fun article about what Freon (brand name) smells like. I asked a lot of people in my industry what they thought refrigerant smelled like. You could read it here.

I know of instances where a motor has burned up due to an electrical short and the fumes that come from a burning motor are:

When non-metallic (combustible) materials undergo thermal decomposition, toxic products are generated. The most commonly occurring of these are carbon monoxide (CO) [12,13], carbon dioxide (CO2), various saturated and unsaturated hydrocarbons (HC), and hydrogen chloride (HCl, for PVC-insulated or sheathed cables), which are accompanied by oxygen depletion.

National center for biotechnology information

Did you notice that this report from NCBI states that carbon monoxide would be present from non-metallic combustible materials when burning? And I’m not scientist, but aren’t we breathing CO2 everytime we inhale, it’s part of Earth’s atmosphere, no?

One of the key points is oxygen depletion. These VOC’s (volatile organic compounds) rob our lungs of good air.

The combustible materials would also be quite limited due to the size of a mini split. The motor in a mini splits indoor unit is very small so the fumes coming from a burning motor would be short lived. Avoid them as much as possible. Throw open all the doors and some windows and call the repairman.

I have to ad, it hasn’t happened to any of the mini splits I’ve installed or serviced. I had one motor fail, but not due to shorted wiring or any type of burning.

Chad Peterson

Chad Peterson is a veteran of the HVAC industry since 1977. "I like to explain heating and air conditioning problems in a way the average home owner can understand. "

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