On an oil fired heating system a firevalve is required by law. The primary reason it is needed is to shut off the fuel supply in the event of a fire near the boiler, so the fire is not constantly being fed by fuel through the pipework.
For domestic purposes the best suited valve would be a capillary firevalve type, these are available in many lengths to fit most circumstances. These are fitted to the outside wall where the fuel line enters the property. Then the capillary tube runs through the building to the boiler where a sensor then monitors the temperature around the boiler, if it exceeds the set activation temperature then the valve on the wall outside is shut off.
Commercial/Industrial situations usually call for a larger firevalve system to be installed such as a drop weight firevalve, these employ a wire and pully system under tension connected to a fusible link that melts and allows the weight to drop on the arm and close the valve. These can also have various electrical components that can notify building management systems such as emergency lighting, doors alarms etc.
The valve body of a capillary firevalve should be fitted on the outside wall where the fuel pipe enters the building. The capillary should then be run around the wall to the boiler and the sensor should be positioned within the boiler cabinet. When ordering capillary firevalves ensure you order the correct length of capillary to reach your boiler.
A Fusible head firevalve is a semi manual firevalve, this means that it can be shut off manually with the handwheel and it also comprises of a soldered link that will melt at high temperatures and shut off the valve.