With over-hot central heating, I needed to crack open a window to sleep; however the asphyxiating coal smog outside irritates my sinuses. Too bad Smartair no longer offers the DIY version with dedicated FAN but Thankfully the SQAIR also operates on its side. Level 1 is virtually silent, Level 2 very quiet, and the Sqair’s gently cooling breezes mean I can sleep without an open window. Recommended