Why Is a Buzzing Furnace Dangerous?

April 12, 2024

No strange sound coming from a furnace should be ignored—but what does a buzzing sound mean? And is it dangerous?

The bad news with a buzzing sound is that it could be for multiple reasons, some of which could lead to uncomfortable or potentially dangerous issues for you and your family. 

The good news is that provided you take the right steps and call a professional furnace repair service to troubleshoot the problem, it can usually be resolved relatively easily,

If you’ve got a furnace buzzing sound, here’s what you need to know about the possible causes, the fixes, and how to prevent your furnace from making strange noises in the future…

Table of Contents

Why is a furnace buzzing sound dangerous?

Furnaces can make a range of sounds, from high-pitched squeals to loud bangs and thwacks. Sometimes, it’s a plain old buzzing sound, which can be annoying and, more importantly, may point to a deeper issue with your furnace that could endanger occupants of the home with an electrical hazard, gas leak or poor air quality. Other times, buzzing noises are simply due to a hard-working furnace with a loose or dirty component, such as a blower fan.

Below, we’ll look at the main causes of furnace buzzing sounds but let’s first consider the main dangers if you hear these sounds coming from your furnace:

Electrical hazards/fires

A buzzing sound may indicate a fault within one or more of the electrical components of the furnace, e.g., a faulty wiring connection to a damaged capacitor or relay.

If the furnace’s in-built safety mechanisms fail, this could lead to an electrical fire and all the associated hazards for occupants.

Gas leak

Most furnaces in Alberta homes are powered by natural gas. A buzzing sound could signify a problem with the gas supply or combustion process, which produces the heat that is distributed around your home.

Most homeowners will be aware of how serious a gas leak can be, potentially leading to health issues, explosions or even carbon monoxide poisoning. 

Poor indoor air quality

Poor indoor air quality can exacerbate many health conditions, including respiratory illnesses and allergies.

Dust and other unwanted contaminants can accumulate in filters and ductwork and enter the home’s heating system if the furnace malfunctions.

A freezing home in midwinter

Another danger of a furnace buzzing noise is your heating system packing up in midwinter, leaving you and your family freezing. This is an inconvenience anywhere in the world but if temperatures are 25 below outside, like in Alberta winters, it’s especially uncomfortable.

The above dangers can be compounded by reduced heating system efficiency and increased energy bills—another possible consequence of a buzzing furnace that can be avoided with regular maintenance.

Why do furnaces make buzzing sounds?

We know how dangerous a buzzing furnace can be—but not all buzzing sounds point to major issues. Some have simple fixes. So, let’s look a little closer at the main reasons for furnace buzzing noises…

Electrical issues

A loose or frayed electrical wire, a malfunctioning relay or a faulty capacitor may all result in buzzing sounds from your furnace. These serious issues may have simple fixes but should be looked after by a professional HVAC technician for safety reasons.

Vibrations from loose components

Something as innocuous as a loose screw can cause a rattle or buzzing sound from your furnace. A furnace contains many moving parts and metal paneling that, over time, can loosen and emit strange noises. Simply tightening screws may solve the mystery buzz, if you’re lucky.

A faulty blower fan motor

One of the prime suspects for buzzing or rattling noises is the furnace’s blower fan, which helps to circulate warm air throughout the home. It could malfunction or develop worn-out bearings. The motor may need lubricating, which is part of a furnace tune-up.

An imbalanced blower wheel

Another problem that can affect the blower fan is an imbalanced or damaged blower wheel. If this happens, it’s highly likely to result in a buzzing or rattling noise and may require repairs or replacement of the wheel.

Obstructions in the heating system

If foreign objects have found their way into the heating system, these can also cause strange buzzing noises (as well as unusual smells). The furnace may need to be opened up by a professional to diagnose the cause of the noises.

Gas valve issues

Any issues involving the gas supply need urgent attention from an HVAC or gas supply professional. One such potential issue for gas-powered furnaces is the gas valve, which can produce buzzing noises if it starts to malfunction.

Ignition system issues

The ignition system in a gas furnace lights the gas burners. A faulty or dirty ignition system may produce unusual buzzing sounds and require cleaning or replacement by an HVAC professional.

Loose ductwork

The buzzing noise in a furnace may not originate from within the furnace itself but be caused by loose ductwork. Warm air passes through ductwork at high pressure on its way to the vents and this can cause loose ducting to vibrate, rattle or buzz.

What to do if your furnace is buzzing

Modern, high-efficiency furnaces run very quietly compared to their older counterparts. You may hear next-to-no sound from the normal day-to-day operation of a well-maintained furnace after some initial startup noises when you turn it on.

Sometimes, with the furnace tucked away in the basement, strange noises are not detected for a while—but subtle, background buzzing noises should not be brushed off. They are not “normal” and should be addressed before they cause deeper issues with your heating system—potentially dangerous ones, as we’ve seen.

There are few things more important in Alberta homes than a safe and efficient heating system. So, if the noises are persistent and more than an occasional annoyance, switch off the heating system and the gas supply, call a professional HVAC technician, and get the furnace checked.

Other strange furnace noises to beware of

Buzzing or rattling aren’t the only strange sounds that can come from a furnace. You might also need professional furnace troubleshooting if any of the following sounds are detected coming from your heating system: 

  • Loud humming
  • Knocking
  • Banging or booming
  • Whistling
  • High-pitched squealing/screeching
  • Clicking
  • Rumbling
  • Any other loud noises

These noises should all be alarming enough to call an HVC professional to investigate—though many have relatively simple fixes that standard maintenance will cover.


Should you fix or replace a noisy furnace?

A noisy furnace can result from so many reasons that it’s impossible to generalize. It’s best to have strange noises investigated by an HVAC professional. Based on the assessment, you can make an informed decision about whether it’s cost-effective to repair the furnace or better to replace it. Most times, noisy furnaces less than 10-15 years old can be repaired.

Why is my furnace making a noise when it’s off?

If your furnace is making a noise when it’s turned off—and won’t turn on again—the issue is typically related to a gas leak or pilot light failure, which activates the inbuilt safety mechanism in the furnace.

Can a noisy furnace explode?

Strange noises and smells from furnaces should always be investigated but the in-built safety mechanisms of modern gas furnaces usually detect gas leaks and mean that disasters like fires and explosions are averted.

How to prevent furnace noises in Alberta

Alberta homeowners don’t need to be reminded about the importance of the furnace in their homes. The cost of a new furnace is returned many times over with a warm, cozy home year-round no matter how bitter the winter gets. That’s priceless!

Looking after your investment with regular furnace maintenance (ideally before the heating season starts) should be a no-brainer. This will help prevent the most common issues—buzzing noises included—in most furnaces most of the time.

During a furnace tune-up, all components are checked, cleaned, and lubricated if necessary and the heating system will be tested for safety, efficiency, and optimal performance.

Our furnace professionals are SAIT-certified and can service any type or brand of furnace in Calgary. Call us at 403-236-4366 or contact us online to book furnace maintenance.

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