In at least one respect, gas furnaces are a lot like many other major appliances around the house these days. Technological advancements, especially in the field of microelectronics, have made them smaller, safer, more efficient and more reliable.

For the owner of a gas furnace, these advancements have also resulted in a more comfortable indoor environment.

As a case in point, consider a development called two-stage heating. According to the Trane Home Comfort Institute, two-stage heating means the gas furnace can operate at either high or low to provide the correct level of comfort with the most efficiency.

The heating experts say you'll feel the benefit of two-stage heating during those transitional seasons that need just a little heat to take the chill out of the air.

Rather than overwhelming you with a full blast of heat, the furnace responds with a pre-heat stage, warming the heat exchangers before circulating air throughout the house. Then, the two-speed blower starts at low speed, quietly and gently warming your home without short-cycling, which is the frequent starting and stopping common to many single-stage furnaces.

In colder temperatures, the two-stage gas valve automatically increases the fuel flow and the blower switches to high speed for maximum comfort. At the end of the cycle, after the fuel shuts off, the furnace continues to run a few seconds, using the remaining heat in the exchangers before shutting off. This ensures that you'll get all the heat you've paid for.

One of the electronic advancements that have made two-stage heating possible is the advent of microprocessor control systems for gas furnaces. Experts at the Trane Home Comfort Institute explain that these state-of-the-art, solid-state control systems act as the furnace's command center, orchestrating each operation with digital accuracy.

They continuously monitor the furnace, insuring combustion and proper gas flow. They also interface with the thermostat to control the furnace system's air flow, venting and two-stage gas valve.

These microprocessors not only control every function of the furnace, they also look for problems in the system. If they find one, they try to resolve it. If they can't, they shut the furnace down and red-flag the difficulty for quick repair when the heating contractor arrives.

In the event of a power failure, "smart" systems even wait patiently until the power is restored and then reset and restart the furnace.