Today I inspected a gas furnace that was 41 years old and still in operation. Average gas furnace life is 15-25 years with proper maintenance. The furnace produced plenty heat but condition not safe to operate.

This furnace had not been serviced in years and  water leak from the humidifier was neglected for some time based on the level of rust to the heat exchanger gas burners and inside of cabinet. The owner is very lucky that nothing serious has occurred such as a heat exchanger carbon monoxide leak or electrical fire from the blow motor if it were to detach from the cabinet and short out the electrical. 

 
The gas furnace was noisy and the whole cabinet vibrated when turned on with normal controls. I shut the furnace down and removed the access panel to find the source of the noise and vibration. The blower motor was being supported with a couple of 2x4. The base of the Furnace was rusted through and not able to support blower motor. Annual maintenance and furnace inspection service is recommend to ensure safe operation.