This is possible due to the optional airbox.

• Healthy, because SNORKEL Technology draws all the necessary oxygen from the outside – just like a snorkel, in fact – and not from your room. That’s important, because the insulation in our homes is constantly improving. SNORKEL Technology ensures the maximum breathing space in even the best insulated homes.
• Safe, because the stoves give off nothing indoors except heat. There is no risk of backwash combustion gases or CO poisoning.
• More efficient, because stoves with SNORKEL Technology no longer suck heated air out of the room.

SNORKEL Technology: for pure heat!