January 1, 2024

HVAC emergencies in St. Louis, MO

Is It an Emergency? Understanding HVAC Urgency

Having problems with your HVAC system is a major cause of stress for most people. Adding to that stress is trying to determine whether the issue you’re having constitutes an emergency or not. After all, no one wants to pay the after-hours or priority pricing for emergency calls.

In the world of HVAC, certain situations will always constitute an emergency because of the safety risks the issues pose. However, there are other situations that may pose an emergency for some households but not for others. Use this guide to unravel the complexity of HVAC emergencies and when it’s worth paying for emergency service.

Specific Smells

When your HVAC system is running well, it shouldn’t produce an odor or smell. There are three types of smells that indicate specific problems and should cause immediate concern and a call for repairs. These include odors like rotten eggs, strong chemicals, and burning. Here’s why each is concerning.

Rotten Eggs

Most people recognize the notorious rotten eggs smell that’s added to natural gas to alert people to a leak. Anyone with gas running to their house should pay particular attention if they encounter this smell.

Do not attempt to identify where the smell is coming from yourself. Rather, get you and your family out of the house and call emergency services and your utility company. Once you get the all clear, the next call is to your trusted HVAC services provider to evaluate your furnace and find the source of the leak.

Strong Chemical

Another disconcerting smell when your furnace is running is that of a strong chemical, some liken it to the smell of formaldehyde. This is a key indication that you may have a cracked heat exchanger in your furnace, allowing toxic fumes into your home. One of the toxic gases it’ll release is carbon monoxide, which can quickly become serious.

If you suspect you have a cracked heat exchanger, shut down your furnace and either leave your home or increase ventilation by opening windows and doors. Once you’re safe, call for an HVAC technician to come inspect your unit. This is one of the inspections commonly included with seasonal furnace maintenance.


A burning smell is fairly normal the first time a furnace runs for a season, especially if you haven’t had your annual furnace maintenance yet. However, that burning smell should dissipate within a few minutes.

If you notice it lingering, getting stronger, is accompanied by smoke, or happens at all with your air conditioner or heat pump, there’s a problem that needs immediate attention. Shut down your system and call for an emergency HVAC repair. Call 9-1-1 first if there’s visible smoke to ensure they can take care of any problems that may lead to a fire.


Like odors, your HVAC system shouldn’t produce much noise as it runs. For both your AC and your furnace, you should have a quiet whirring of your circulating fan. Your AC will also have the sound of the condensing fan outside and the hum of the compressor. Your furnace may also produce a quiet whoosh when it first fires up. Other sounds may indicate an issue, but two are of particular concern: loud banging and rattling when a furnace is first starting up.

Loud Banging

There are a number of problems that can cause loud banging in your system, including flexing metal ductwork. However, when the banging seems to originate from within your furnace during a heating cycle, there’s potentially a major problem. This sometimes happens when there’s an ignition problem, allowing gas to build up in the burn chamber and ignite with a higher concentration. This not only poses a risk to your furnace but can also become a fire hazard for your home if there’s a substantial enough delay and accumulation of fuel.

Rattling During Furnace Warm-Up

Rattling can indicate a problem with a loose component in the system, something you want to have repaired, but isn’t usually an emergency. However, when that rattling only occurs when your furnace is starting up, it may indicate a cracked heat exchanger. This happens because the metal in the heat exchanger expands as it warms up, causing the rattling. Once it’s fully heated, it may stop rattling. If you hear this, call to have a technician inspect your heat exchanger.

Carbon Monoxide Alarm

A properly functioning carbon monoxide alarm will alert you before the concentration of carbon monoxide becomes dangerous in your home. The most common source of carbon monoxide in homes with furnaces is a cracked heat exchanger. If your carbon monoxide alarm goes off, get your family out of the building and call to have a technician inspect your furnace for leaks.

Electrical Issues

Electrical issues can happen with any HVAC equipment and can pose a risk of harm and fire if not properly handled. Common issues include exposed wires, circuit breakers that repeatedly trip, and arcing. If any of these are apparent with your HVAC system, shut it down and call to have a technician inspect and resolve the issue.

No Heating or Cooling During Extreme Temperatures

Not getting heat or cool air from your HVAC system is not always an emergency, depending on the temperature outside. When there are frigid temperatures in the winter or sweltering heat and humidity over the summer, it can become an emergency, especially if someone physically vulnerable lives in your home. As you consider whether to treat this as an emergency, consider whether you have another place you can stay, or if the temperatures are extreme enough to pose a danger to your family.

Other Possible Emergencies

There are many other problems you may encounter with your HVAC system, many of which you can tackle as a standard repair. However, there are two that may become an emergency, depending on your home situation.

Water Leaking Around Your Unit

Water leaking around your unit means that it’s producing more condensate than it can effectively drain. This can be a problem with a clogged drain line or may indicate a cracked heat exchanger on your furnace or one of several possible problems with your AC. The end result is that it may cause your system to shut down prematurely. If this falls at a time when it’s dangerous for your family to be without heat or cooling or if it’s accompanied by one of the other issues already discussed, you may want to treat it as an emergency.

System Icing

Air conditioners and heat pumps may freeze up for several reasons, but it will cause them to ineffectively cool or heat your home, if not shut down entirely. If this happens during extreme temperatures, you may want to treat it as an emergency and have a technician quickly come find the underlying problem.

For more than 40 years, people around St. Louis have turned to Scott-Lee Heating Company to keep their homes comfortable and safe. Our award-winning team provides AC and heating repair, maintenance and installation along with indoor air quality solutions and HVAC zoning. Call to schedule your heating or AC repair with one of our NATE-certified technicians today.