BS 5864:2019 Installation and maintenance of gas-fired ducted air heaters of rated heat input not exceeding 70 kW net (2nd and 3rd family gases). Specification

Selection
Commissioning
Siting
Ratings
Maintenance
Gas space heating
Ducts (building services)
Household equipment
Heaters
Fan-assisted warm-air heating
Heating equipment
Flued heaters
Gas-powered devices
Heat
Installation
Central heating
Domestic
Thermostats
Warm-air heating
Air heaters
Inspection

Link: BS 5864:2019 Installation and maintenance of gas-fired ducted air heaters of rated heat input not exceeding 70 kW net (2nd and 3rd family gases). Specification
Source: BSI Standards