Your safest bet is to check with your HOA and/or property manager & clear the use of an upright barrel smoker with them first.  To be honest if you live in a condo or apartment complex where there are units above yours, and to the sides the smoke involved will probably disqualify you from being able to use something like this in that type of setting.  It’s usually too close for comfort in a situation like that.  However, if you have a top floor unit you just might be able to make it happen!  In terms of radiating heat doing any type of damage these types of cookers don’t get any hotter than your standard big brand name gas or charcoal grill when used as intended.  If any danger should present itself it would be through operator error resulting from either a grease fire from irregular maintenance or leaving the lid open for too long with full draft (refer to question above about catching fire).  If your HOA/property management were to clear you, then common sense should be applied in operating your drum safely and responsibly.  If you’ll be operating your drum on a balcony, ensure that the surface is made of a non-flammable material like stone or concrete.  For the condo/apartment setting, since the heat source is at the bottom of the drum it would be best to create a barrier between the drum and the surface as a precautionary measure just in case.  Having it on wheels or sitting on some type of raised platform such as block or brick if it doesn’t have wheels would be a better idea than it just sitting directly on the balcony.  This would be for better ventilating of any radiating heat between the drum and balcony surface.  Or you could invest in a fire pit pad.  Even though heat doesn’t travel downwards it’s just a safer bet this way.  Since drums do come with a way to transport them or the option thereof, wheels for example, you can always just “store” the drum on your balcony, and set it up in a common area when you want to use it if they won’t allow balcony usage.  Functional areas of the property like parking lots, swimming pool areas, and parks.  If you do get the clearance for balcony usage, then a suggestion would be to make sure your neighbors know about it, and are cool with it.  Don’t want to be putting them on high alert with the smell of smoke, let alone smoking them out of their own homes!  To reiterate…. make sure you get the OKAY from your HOA and/or property management first.  Read more about using a barrel cooker on a condo or apartment balcony