Seems like its for garages and shops? They aren't too upfront with how much ventilation is required.. I already have a carbon monoxide detector in the garage so I guess rely on that and whether you pass out or not?
https://www.farmandfleet.com/products/786261-dewalt-portable-radiant-heater.html
https://www.farmandfleet.com/products/786261-dewalt-portable-radiant-heater.html