Maintenance engineers handle repairs and routine maintenance of mechanical equipment in one or more buildings. As a maintenance engineer, your duties include working on boilers and cooling systems, replacing broken parts and filters, painting, patching drywall, and fixing electrical or plumbing issues. As you gain experience, you deal with more technical or complex jobs. Depending on your employer, you may have the option to specialize your skills in one area, such as plumbing, electrical, or HVAC (heating, ventilation, and air conditioning) systems.