ZWS13 door viewers may be fitted to previously tested (or assessed by warringtonfire) fully insulated timber doorsets, to provide up to 60 minutes integrity performance if tested in accordance with BS 476: Part 22: 1987 or BS EN 1634-1: 2000. WF Assessment Report No. 303317 Issue 2 dated 11.01.2011 and WF Report No. 361830 dated 12.02.2016 refer. Copy available upon request. No intumescent is required on 30 minute doors but a 1mm thick 54 x 50mm intumescent wrap is required on 60 minute doors to provide additional protection, ref ZWS13/WRAP. When using a wrap it will be necessary to increase the bore size to 15mm.