Killer furnace

We got quite the shock this week when all the smoke alarms in the house started going off when the heating came on. The furnace was quickly shutdown and the heating guy called out. It turned out a sizeable hole has appeared in the heat exchanger​ resulting in the burning gas escaping into the house heating duct instead of going out the flue. Luckily someone was home when this happened and the house is still standing. If the fire hadn't got us the carbon monoxide would have!