Thanks to the rise in air conditioning across the nation over the last 50 years, American researchers found the chance of dying on an extremely hot summer day has decreased by more than 80%. But if your air conditioner stops working this summer, you may feel like you’re dying! If you want to avoid waking up or coming home to an unwelcome surprise — namely, a sweltering hot house — this season, regular HVAC repairs and maintenance are a must. And if you want to know whether emergency heating and air service might be imminent, look for these three surefire signs.

1. Weak airflow or opposite temperatures
When your HVAC system suddenly produces a weak airflow or one that’s of the opposite temperature — meaning hot air coming out of your cooling vents or cold air from your heating system — it’s time to call for emergency HVAC service. This could be due to a number of issues including blockages and problems with your ductwork. A professional will be able to tell for sure. It’s important that you call for emergency heating and air service right away, though; otherwise, it could lead to a total system failure.

2. Strange sounds or smells
You might not think much of a weird noise or odd odor coming from your cooling or heating unit, but you should definitely be on alert if you notice either. Usually, strange sounds will occur when a particular component becomes damaged. If left unchecked, these malfunctioning parts can cause your HVAC system to stop functioning altogether. And should you smell a plastic or foul odor, it may be due to burning wires or other serious issues. You should shut down your HVAC system and call a professional immediately, in these cases.

3. No response
The most obvious sign you need emergency heating and air service? Turning on your air conditioning or heating system with no response. While this situation is rare, it can happen — and it usually does at the worst possible time. This is indicative of a serious HVAC issue and needs to be fixed right away. Typically, it signals a large problem with your system’s inner workings. It’s vital that you contact your technician if this happens to you.

As long as you schedule regular maintenance checks every year and care for your system properly, you should be able to avoid disasters like these. But if you do spot these signs, be sure to call your emergency HVAC technician as soon as possible.