Hi Leee!

With opening doors, I reckon if the door has time to shut before the person arrives, it's OK to let it close. BUT with security doors, they're security for a reason, so I never hold them open unless it's a friend I'm walking with. I don't want to let an unsecured person into a security-protected zone, IYKWIM.
Hi there Lady Zaidie

Yeah that's kinda how I treat it although I can't help but feel guilty even when they are a fair distance away and I let the door close...