They are rarely used outside of ships and vehicles in the UK as they aren't recognised as an acceptable means of fire protection, you see them used more in Ireland and Spain and similar, so there isn't loads of guidance out there.
Based on various sources I can find and the linked, it's mounted above the hazard at a height from the floor in the range of 1.5 - 3m https://www.emme-italia.com/sites/default/files/librettotecnico/13069-3_13129-3_Technical manual.pdf