Double Vent
Double Vent

Screen on outside

Airvent
Airvent
DV with sleeve
DV with sleeve
hopper
hopper

VENTS            Air vents :  have screens  on the outside and  a door  that opens on inside

                                                       Dryer vents:  are used for exhaust purpose with louvers on outside

                                                    Hoppers  :  are used for a fire  escape  and can also be used for ventilation