Extinguisher sets are sold as bundles: two or three units, a blanket, brackets, signs and sometimes a stand. They are a convenient way to buy and a poor way to decide. What a building needs is set by its fire risk assessment, which names the fuels present room by room, and then by how far anybody has to walk to reach a unit.
What drives the count
Travel distance, not floor area. The provision is arranged so that a person does not have to walk far, and never towards the fire, to reach an appropriate unit. In practice that puts extinguishers at exits, at stair landings and at the specific risks, and it means a long thin building needs more units than a square one of the same area.
What drives the type
The fuels in each space. A room with paper needs class A cover. A store with solvents needs class B. A kitchen needs class F. A switch room needs carbon dioxide. A bundle chosen from a catalogue matches none of these except by accident, which is why a set is a shopping list and not an answer.
Where a bundle genuinely helps
A small single occupancy unit with one obvious risk profile, where the assessment has already concluded that two class A units and a blanket at the kitchenette is the whole provision. Buying that as one item with the signage and brackets included saves time and gets the signage fitted, which loose purchasing often does not.
The parts people forget
Brackets or stands, because an extinguisher on the floor gets moved and then blocked. Signs above each point, because a person under stress looks up. A location on the fire plan, so the assessment and the building agree. And the entry in the log book, so the monthly check has something to check against.
Questions people ask about fire extinguisher set
Is a fire extinguisher and blanket bundle enough for a small office?
It can be, if the assessment says so. The test is whether every fuel present has an agent rated for it within a short walk, and whether anybody has been told which unit to use.
How many extinguishers does a small premises need?
There is no fixed number in law. The provision has to be appropriate to the risk, and the practical driver is travel distance to a suitable unit from anywhere a person might be.
Should a set be bought before or after the risk assessment?
After. Buying first tends to produce a provision that the assessment then has to work around, and over provision is as common an outcome as under provision.