Generally speaking, these types of heaters are used in industrial environments and are ideal for heating a specific area of a workshop, factory floor or garage.  It is worth mentioning that whilst these heaters will run on a fossil fuel, they do still need to be plugged into an electric power source to run the fan.

Pros

Fossil fuels such as diesel, kerosene and paraffin are more fuel efficient and longer lasting, offering a much higher output than other heater types such as electric and infrared. They average from about 10,000 BTU/hr to  200,000+ BTU/hr, allowing you to heat huge areas with ease.

Cons

The main disadvantage to this type of heater is that they need to be situated in a large well-ventilated area because of the emissions produced. Additionally, although they can be used in a domestic environment, it is worth noting that these heaters can get extremely hot and so caution must be exercised if young children are close by.

Electric heaters are the most common type of space heater and are popular for heating specific rooms or small areas

Pros

Standard electric heaters that operate between 1kw -3kw range are cheap and efficient to run (on average around £0.40 per hour). Electric space heaters use radiant heating methods and are best suited to the heating of a specific area or object.  Typically electric heaters range between 1-3Kw although higher outputs can be purchased such as the Turbofan 9000 (9Kw) which will require 3-phase electric.

Cons

They are ineffective at heating rooms like convection heaters, however they do provide fast and effective heat to specific areas.

Infra-red heaters emit infrared light into a room or space to create heat on the objects it touches. These heaters can be known as combination heaters as they can be classed as both radiant or convection heaters, depending whether they have fan assisted outputs. They differ from conventional heaters where they don't blow hot air at objects rather, they emit hot light and objects absorb the light such as your skin and clothes, hence they tend to have more warming effect when in close proximity.

Pros

Because of their operation infrared heaters are perfect for heating small spaces such as a workshop bench or a pub beer garden where the end goal is to provide heat to the person or object as opposed to heating the room.

Cons

Infrared heaters are not good at heating the air (only the objects they are directed at) and so if this is the goal you have in mind then you should consider another type of heater.