We have a 2 floor hair salon we've just opened  and we have to install fire equipment but I'm not sure which extinguisher will do the best. 

Let me explain the fire risk present on here:

Class A:very likely to have such as fabric paper or wood is very present here. 

Class B:not common but can happen, 

Ej:paints, hair ink, aerosols, and so on

Class C:unlikely 

Class F:uncommon

Live electrics:very common as we use lots of electric machinery. 

Water ones are good but I dismiss them as they cannot fight flammable liquids. 

AFFF and co2 would be great but dry powder is not a bad idea 

Is there any problem indoors against law with British standard? (or simply not recommended) thanks for solving all my doubts. 

Hi, I would totally dismiss powder in this situation. The reduction in visibility and the risk of inhalation when used indoors is just too big.

I would recommend water mist extinguishers (with de-ionised water), which can be used on these risk, including the electrical risks (de-ionised water does not conduct electricity).

Harry

Powder also risks wrecking the salon and equipment. Water mist simplifies cover as you only need one type, halving the number you need and making it easier from a training point of view.

Water mist is safe on flammable liquids, but only small fires hence the lack of Class B marking on them, but the small quantities liable to be involved in your type of premises should still be covered. 3 litre mists have a 13B rating, 6 litre mist a 21B rating.