This is a must. Gas furnaces that are not in proper working order kill hundreds of people every year through fire or carbon monoxide poisoning. All homes should have working fire detectors and carbon monoxide detectors. Having these is still not enough, your furnace must be inspected by a qualified technician every year. The technician will test all safeties to ensure the furnace will shut down if it has any problems, check gas lines for any leaks, check the vent work for proper flow, and the heat exchanger for any cracks. This will provide you with a peace of mind that your furnace is not a hazard.