13 ENVIRONMENT. HEALTH PROTECTION. SAFETY 13.040 Air quality 13.040.40 Stationary source emissions 23 FLUID SYSTEMS AND COMPONENTS FOR GENERAL USE 23.120 Ventilators. Fans. Air-conditioners27 ENERGY AND HEAT TRANSFER ENGINEERING 27.060 Burners. Boilers 27.060.10 Liquid and solid fuel burners 27.060.20 Gas fuel burners 27.220 Heat recovery. Thermal insulation91 CONSTRUCTION MATERIALS AND BUILDING 91.060 Elements of buildings 91.060.40 Chimneys, shafts, ducts 91.140 Installations in buildings 91.140.10 Central heating systems 91.140.40 Gas supply systems 97 DOMESTIC AND COMMERCIAL EQUIPMENT. ENTERTAINMENT. SPORTS 97.040 Kitchen equipment 97.040.20 Cooking ranges, working tables, ovens and similar appliances 97.080 Cleaning appliances 97.100 Domestic, commercial and industrial heating appliances 97.100.01 Heating appliances in general 97.100.10 Electric heaters 97.100.20 Gas heaters 97.100.30 Solid fuel heaters 97.100.40 Liquid fuel heaters 97.180 Miscellaneous domestic and commercial equipment |