For larger premises, such as a car dealership that has a showroom, office, workshop, store and flammable storage, you need to break this down and consider each area on its own. However, it is best not to have too many different types on the same premises if possible as this adds to confusion in a panic. So, if you have foam in the workshop, use a foam fire extinguisher as the water-based one in the office area.
Should your premises have multiple risks such as a garage workshop, a powder fire extinguisher may be better as your fire may include wood, paper, paint and fuel all at the same time. In a garage workshop we would recommend powder for general use and CO2 for small welding fires but the office area would still need water-based ones as powder will make a mess. In an office, hotel or nursing home, powder would make a dust cloud that may stop people from finding exits.
A commercial kitchen should have a combination of fire blankets, wet chemical extinguishers for any deep fat dryers, plus C02 for electrical fires. An office would have the same risks as most shops, salons, hotels, residential homes, shopping centers, etc. so the requirements would be a water additive extinguisher with a CO2 at each fire point. Construction sites would have multiple risks so powder and CO2 would be a good option.
Don’t forget a fire extinguisher in company vehicles – every vehicle should have a 2kg powder extinguisher in the driving area, and larger vehicles carrying dangerous goods require further fire extinguisher provision.
Another consideration is the temperature. So, if they are stored outside on a petrol station forecourt or building site, powder would be best as it can be used down to minus 30 degrees. Foam and water would beat antifreeze but this reduces the fire-fighting ability and, by the time an engineer visits, discharges and refills with antifreeze, will probably cost more than you paid to buy a new extinguisher!