A "heater vent" is a metal or plastic opening in a wall or floor that allows warm air from a heater or furnace to come out and heat up a room. Full definition
However, it takes about 20 minutes for hot air to come out the front heater vents when the heater is set to maximum heat and the fan is on. (mechanics.stackexchange.com)
As soon as I jumped in the car I just couldn't look beyond the silver coloured plastic heater vents, pretend leather on the dash, the lunchbox plastic trim next to the front seat belts, and shiny silver plastic switch gear.... (evo.co.uk)
It even has a Vintage Air A / C unit built into the center glove box and heater vents where the former ashtrays used to reside — plus some cool retro dummy lights that all look original. (automobilemag.com)