What counts as an HVAC emergency?

Not every HVAC problem needs a midnight call — but a few genuinely can't wait. The test is simple: does the situation threaten someone's safety, someone's health, or the home itself? If yes, treat it as an emergency. Here's how the most common scenarios sort out across the GTA and Hamilton.

Call right away — these are true emergencies

• Any gas smell (rotten-egg odour): this comes first. Don't touch switches or phones indoors — leave the building, then from outside call Enbridge Gas at 1-866-763-5427 or 9-1-1. See what to do if you smell gas.
• Suspected carbon monoxide — a CO alarm sounding, or flu-like headache/nausea/dizziness that eases when you leave the house: get everyone, including pets, to fresh air and call 9-1-1. More on furnace CO risk.
• No heat in winter, especially below freezing: an unheated GTA home can reach pipe-bursting temperatures within 12–24 hours.
• A major water leak from the furnace, AC, or water heater that's pooling or spreading toward electrical or finished space.
• No cooling during a heat warning when infants, seniors, or people with medical conditions are in the home — heat illness is a real risk.
• Repeated breaker trips or any burning/electrical smell from the equipment — shut it off and call.

Usually safe to wait until morning

• Weak or reduced airflow while the system still produces some heat or cool air
• One room that's colder or warmer than the rest of the house
• Equipment that's noisier than usual but still running normally
• AC out on a mild day with no heat warning and no vulnerable occupants
• No hot water — uncomfortable, but rarely damaging to wait 12 hours

The grey areas

Some calls fall in between. A small drip from the AC during cooling season can often wait a day, but a furnace leaking water in winter shouldn't. Loud furnace noises like banging on startup or grinding warrant prompt attention even if the unit still runs. When in doubt, call the 24/7 line and describe what you're seeing — a good dispatcher will tell you honestly whether it can wait.

ZK Mechanical answers around the clock with no overtime surcharges, and we'll give you a straight answer about urgency before dispatching. If it's a real emergency, call (647) 801-1252 for 24/7 emergency HVAC service; if it can wait, contact us to book a same-day or next-day visit across the GTA and Hamilton. Many emergencies are prevented entirely by a maintenance plan.