From 1st January 2022 a 4-litre plumbed extinguisher will be obligatory for circuit racing in the UK. So if you are fitting out a new car for racing or buying a new extginguisher because the old one is not accepted by the companies that service and refill them, then it is advisable NOT to buy one of the present 2-.25 litre ones. If you do, you will have to throw it away after next season. You will also have to throw away the 6 mm piping because 8mm nozzles and tubing are likely to be obligatory.
The MSUK regulations (Blue Book) ar given in full at https://www.motorsportuk.org/wp-content/uploads/2019/12/Blue-Book-2020-1.pdf
In addition to the regs on fire extinguishers shown below, Motorsport UK replied in February 2020 to a request for clarification:
“The minimum capacities for Small, Medium and Large extinguishers referenced in K3.1.2 are detailed in Table 3 on Page 176. For Circuit Racing 3.1.2(a) applies which is a minimum capacity of 2.25 litres AFFF. These minimum capacities apply to non-homologated extinguishers. For FIA homologated plumbed-in extinguishers (mandatory from 1st January 2022) the minimum capacity is defined by each individual system’s FIA homologation [note from Marcus Bicknell; which is 4 litres]
Hope this helps.
Michael Duncan, Technical Manager, Motorsport UK https://www.motorsportuk.org/ “
Excerpt from MSUK, July 2020: Fire Extinguishers
Existing vehicles competing prior to 1st January 2019 may comply with the following until 1st January 2022. Newbuild vehicles from 1st January 2019 must comply with Appendix 3.
3. A fire extinguisher/extinguishing system must be carried on all vehicles, the minimum requirement being that the system be charged with one of the permitted extinguishants and be operable by the driver whilst normally seated either by manual operation or by a mechanically/electrically assisted triggering system. All extinguishers must be serviced in accordance with the manufacturers guidelines, or every 24 months, whichever is sooner.
3.1. Capacities. Extinguishers are classified as Small, Medium or Large, and designated as Hand-Held or Plumbed-In. Drypowder extinguishers are prohibited.
3.1.1. Small, Hand operated. [1.75 litres]
3.1.2. (a) Medium, Plumbed-In, for discharge into both cockpit andengine compartment. [2.25 litres]
(b) Medium, Hand-Operated, for discharge into both cockpitand engine compartment. [1.75 litres]
3.1.3. Large, Plumbed-In, for discharge into both cockpit and engine compartment. [2.25 litres]
3.1.4. Large, Plumbed-In, [2.25 litres] for discharge into Engine compartment, plus Medium, [1.75 litres] Hand-Held for Driver or Rally Co-driver use.
3.1.5. Hand-operated for cockpit (International). [2.4 litres]
3.1.6. Permitted Extinguishants. AFFF, ZERO 2000. (SeeTable 3.)
Copies of the list of FIA/MSA approved plumbed systems areavailable from Motorsport UK.
3.2. Plumbed-In Systems(If AFFF they must be FIA/MSAhomologated).
3.2.1. The Large unit should have two points of triggering, one for the driver (and Co-driver in Rallies) and one outside thecar for activation by Marshals etc.
3.2.2. The triggering point from the exterior must bepositioned close to the Circuit Breaker (or combined with it)and must be marked by the letter “E’’ in red inside a whitecircle of at least 10cm diameter with a red edge.
3.2.3. In installing units, the direction of nozzles should becarefully considered, Induction, Exhaust, Ignition and Fuelpumping systems being the most likely areas for fire to occur.
3.2.4. Where possible sources of fire exist outside the engineor cockpit areas (i.e. front mounted fuel tanks) advice can besought from Motorsport UK concerning plumbed-in systeminstallations.
3.2.5. All bottles should discharge simultaneously and mustbe operable in any position of the car even if inverted.
3.2.6. The fitting of a pressure gauge is recommended(mandatory for pressurised AFFF units).
3.2.7. Method of Operation: The preferred methodof operation is electrical which should have its own source ofenergy for triggering, ideally with provisionfor checking the integrity of the systems triggering circuit.
3.2.8. Mechanically operated systems, if used, should befitted with ‘Total Discharge’ valves (i.e. ones that continue to discharge even if the operating mechanism should fail after triggering. Hand-held extinguishers which have been adapted,by addition of pull-cables, rarely have the capability of being operated in varying positions and are not acceptable.
3.2.9. Weight checking: Extinguisher systems should becapable of being dismantled for the purpose of checking theweight of the extinguishant and the integrity of the cylinder, also to enable the operating system to be serviced withoutdischarging the contents. The tare weight of the unit must be marked on the cylinder.
3.2.10. Installation: Particular attention should be paid to the installation and maintenance of any system, especially if it is mechanically operated. Pull cables should be fitted in such away that no kinks or ‘S’ bends are formed which could causemalfunction.
3.2.11. A list of plumbed-in extinguisher kits that are approved by Motorsport UK is available on request.
3.3. During events:
3.3.1. All plumbed-in extinguisher systems must be in an‘ARMED’ condition (i.e. be capable of being operated withoutthe removal of any safety device) at all times whilst competing or practising in races or speed events (including during post-event scrutineering), and at all times that crash helmets are worn on rallies (i.e. on Stages etc.).
3.3.2. Any plumbed-in extinguisher system found to be incapable of being operated will be the subject of a report to the Clerk of the Course/Stewards for possible penalty as an offence against Safety Regulations.
3.3.3. Checking for correctly ‘Armed’ extinguisher systems,should only be carried out by Motorsport UK Scrutineers, and/orJudges of Fact nominated for that purpose.
3.4. Hand-held extinguishers
3.4.1. Must not be carried loose but should be retained inpositive quick release brackets, secured to the vehicle by aminimum of two 6mm bolts.
3.4.2. Extinguishers with pressure gauges are recommended.
3.4.3. The tare weight of the unit must be clearly marked on the cylinder.
3.5. GeneralIy it is recommended that all fire extinguisher bottles be securely mounted within the main structure of the vehicle. It is prohibited to mount bottles of over the medium capacity outside the main structure.