The Simply Silent CV4S Fan from Xpelair is a two speed, constant volume fan with an intermittent hour-run on timer which is suitable for wall, ceiling, window and panel mounting. This Simply Silent fan incorporates Ghost Airflow Technology which offers all of the following benefits.              Flow straighteners guide air through ducting which reduces turbulence, smoothing and making the air flow laminar.     A cone reduces turbulence in front of the fan and air is directed straight into the impellor     Ball-bearing motors suppress noise from the motor For ease of installation             Strengthened ducting reduces duct distortion on fitting and avoids breakage     Radial screw slots for easy alignment of back plate prior to final fixing     Features a level line at bottom of back plate for ease of alignment     Large cable access for ease of wiring     Front cover is easy to remove or replace     To replace  - hook at top, rotate, press and clip back into place     Notch to remove cover with tool - no screws     Easy cleaning thanks to twist and turn baffle It is finished in white and boasts a modern discreet design which will complement even the most exacting decor and environmental requirements. The fan is IPX4 rated and meets Building Regulations Part F.