• Do maintain and prolong your furnace by cleaning air returns with a household vacuum cleaner and checking the filter once a month and replacing it if necessary. 
• Do get your heating system thoroughly cleaned by a reputable, licensed, local mechanical contractor every two years. 
• Do get at least three independent written estimates from licensed local mechanical contractors if a furnace repair or replacement is recommended. If you subsequently sign a contract for work, make sure it stipulates that your final payment will be withheld pending mandatory inspection by the building department responsible for mechanical code enforcement where you live. 
• Do ask to see the mechanical contractor's license and write down the contractor and license number listed on it. 
• Do verify that the license is valid and holds the proper classifications for the work he or she will be conducting for you. You can check this information by visiting the Bureau's website at www.michigan.gov/bcclicense or by calling the Bureau's Mechanical Division at (517) 241-9325. 
• Don't fall for telephone solicitations that offer "low-cost" or "free" furnace cleaning. Once in the dwelling, the worker will tell the homeowners their heating system has serious problems that require immediate attention. 
• Don't sign a contract just because the worker says you face possible illness or death if the furnace isn't replaced immediately. If told your furnace threatens your health, ask for a written copy of the technician's test results and call your local gas company. 
• Don't hire someone who comes to your door with a Shop-Vac vacuum offering to clean your heating ducts. It won't do the job. A proper cleaning requires a high volume vacuum system and maybe even a steam process.

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