Choosing where equipment goes, and keeping the area around it safe. The wrong location can create an ignition source, a shock hazard, or a chemical exposure.
Use of equipment in an unsuitable environment can cause ignition or explosion. Make sure the equipment’s hazardous-location classification matches the area it is installed in.
Areas where flammable gases, vapors, or dusts may be present are classified by code, for example under NEC Articles 500–506 in the United States or the IEC 60079 series elsewhere. Equipment in those areas must be listed for that classification. Standard controllers, relays, WiFi devices, and motors are not, unless their documentation says so.
If you are not sure whether an area is classified, ask the site owner before installing anything.
Plant rooms, boiler rooms, and cooling towers are wet. Use enclosures rated for the location, keep cable glands sealed, and use GFCI protection where your code requires it. See Electrical Safety.