system using special tools / metal / fiberglass ducts / water-based heating systems / metal snips / or repair cooling and heating systems / program control systems / transport food / maintenance services / Refrigeration systems / refrigeration equipment / forced air heating systems / climate-control equipment / Appropriate safety equipment / air-conditioning equipment / heavy equipment / oil / refrigeration technicians service equipment / retail establishments / test equipment / sheet metal workers / combustion test equipment / air-conditioning systems / industrial and commercial refrigerating systems / /