• Do maintain your furnace by cleaning air returns with a household vacuum cleaner and checking the filter once a month and replacing it if necessary. This will maintain efficiency and prolong the life of the furnace. 
• Do get your heating system thoroughly cleaned by a reputable, licensed, local mechanical contractor a minimum of 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 final payment is not due until the mandatory inspection by the mechanical code enforcing agency is approved. 
• 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 issued for 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 http://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 may tell the homeowners their heating system has serious problems that require immediate attention. Get a written description of the suggested work and seek a second opinion. 
• 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 utility company. 
• Don't hire someone who comes to your door with a Shop-Vac vacuum offering to clean your heating ducts. It will not do the job. A proper cleaning requires a high volume vacuum system and maybe even a steam process.

Read more releases from the Michigan Department of Energy, Labor & Economic Growth