Extract danger | Archive Titles

TR17 summary of recommendations
Maximum permitted contamination of internal surfaces of extract ductwork	6 g/m2 (Vacuum test) 180 mm (Deposit thickness test)
Frequency of cleaning kitchen extract systems (dependent on usage of cooking equipment)	Heavy use (12-16 h per day): 3 monthly Moderate use (6 -12 h per day): 6 monthly Light use (2-6 h per day): annually
Factors to consider when selecting a specialist contractor for extract ductwork cleaning	Experience – years in business, track record and number of operatives; Affiliation – membership of bodies such as the HVCA and NADCA; Quality assurance; Health and safety – policy, records of training, accidents and awards; Insurance – professional indemnity, public and employers’ liability and all-risks; Financial – competence to handle contracts of proposed size.
Size of access panels to be located every 3 m in horizontal circular ducts	Duct size (mm)	Opening size (mm)
	200	300 x 100
	500	400 x 200
	1000	450 x 450
	Duct entry	600 x 500