Small extinguishers, typically one or two kilograms of dry powder, are sold for cars, caravans, boats and home use. They are genuine tested products and they are frequently bought for places they do not suit, because the price is low and the shape is convenient. What limits them is not the agent but the quantity of it.
Discharge time is the real constraint
A small unit runs for a very short time, measured in a handful of seconds rather than tens of them. That is enough for a fire caught in its first moments in a confined space, and it is not enough for anything that has spread to a second item. The rating printed on the label reflects the size of test fire it extinguished, and small units carry small ratings.
Where they belong
In a vehicle, where the risk is an engine bay or a small interior fire and the alternative is nothing at all. On a boat or in a caravan for the same reason. Beside a specific small risk where a larger unit cannot be sited. In each case the unit is buying time to get out, not a means of fighting a developed fire.
Where they do not
As workplace provision. A one kilogram unit mounted in a workshop looks like compliance on a plan and will not meet the rating the risk assessment called for. Where an assessment specifies a class B rating, the replacement has to meet that rating, and small units generally do not.
Powder in a vehicle, with a caveat
Powder is the usual agent at this size because it is rated widely and is unaffected by cold. In a car cabin a discharge removes visibility instantly, so the technique is to discharge into the engine bay through a gap rather than to open the bonnet fully, and then to move away.
Questions people ask about fire extinguisher 1kg
Is a small powder fire extinguisher any use at all?
Yes, for what it is designed for: a very early fire in a vehicle or a small enclosed space. It is a poor substitute for a properly rated workplace unit.
Do small units need servicing?
Any extinguisher provided for use at work is work equipment and has to be maintained. Vehicle units sold for private use are usually replaced rather than serviced, and they carry an expiry on the label.
Can a 1kg unit satisfy a fire risk assessment?
Only if the assessment specified a rating it meets. It cannot be substituted for a larger unit on cost grounds without revisiting the assessment.