Not all divers will get a satisfactory seal from the skirt of any given full-face mask, as face shapes and sizes differ, but most divers will be able to find a mask that works for them. A major flood caused by a temporarily dislodged mask is easily drained by purging after replacing it in the correct position, and adjusting the straps if necessary. Lesser leaks will usually drain automatically from the mask through the exhaust valve of the demand valve or a purge valve fitted for that purpose as long as the mask is orientated with the valve at the low point. If there is too much water in the mask to allow inhalation it can usually be cleared using the purge button on the demand valve.