All operational grease extract ductwork systems will require cleaning annually as a minimum unless a fire risk assessment recommends otherwise.
The following factors have an impact on the frequency of cleaning:
Pre-cleaning micron readings are taken to enable cleaning frequency to be confirmed as suitable or adjusted accordingly. To verify frequency of cleaning based on micron readings it is recommended that inspections be carried out at regular intervals. The table below sets out guideline maximum levels of grease deposit and actions recommended.
Surface Grease Deposit Limits
|WFTT Measurement||Recommended Action|
|200µm as a mean across the system||Complete Cleaning Required|
|Any single measurement about 500µm||Urgent Localised Cleaning Required|
|Cleaning Intervals (months) Daily Usage|
|Perceived level of grease production||Typical Example||Daily Usage: Up to 6 hours||Daily Usage: 6-12 hours||Daily Usage: 12-16 hours||Daily Usage: 16+ hours|
|Low||No significant production of grease laden aerosols during normal daily food production operations||12||12||6||6|
|Medium||Moderate production of grease laden aerosols during normal daily food production operations||12||6||4||3|
|High||Heavy, significant or continual production of grease laden aerosols during normal daily food production operations||6||3||3||2|
Insurers may not always pay a claim if the duct system was found to be the cause of the fire spreading, especially if it could be demonstrated that the system was not properly cleaned in accordance with their policy conditions or warranties.