Yeah im agreeing with above. Theres so many variables that theres not gonna be a single answer. Whats the ROA? Whats the specific opiate? Are they taking other drugs? Whats their tolerance like? So many things are going to change that. If they blast a good ass bag, nod out for 10 minutes then get up and head out, are they gonna be alright? Maybe, you cant really say for certain. In my experience with things with high potency and shorter half life i was good if i didnt go down within 30 minutes, but ive seen plenty of other people blast a bag of fetty, walk out of a bathroom, go outside, smoke half a cigarette and then just fall over. Like Keif said its best to just live like every situation could lead to that so you're always vigilant. Always have narcan on hand and always watch out for each other, and if you're gonna be using alone try to make sure someone else knows what you're doing so they can come check up on you.
I had a friend die because of that exact scenario. She od'd in a house full of people because she didnt tell anyone else she was using, so when someone checked up on her a bit later and peaked in and she was just laying in bed curled up like she was napping, no one thought any different. But after hours passed and she didnt come down her boyfriend went to see if she was still asleep and found she had taken a shot, laid down to enjoy herself and went out. Had she warned him or anyone else in the house she was going to use and to check up on her they could have made sure she was alright. Its pretty easy to fall through the cracks. My brother od'd in a similar manner, he got some shit and brought it to his overnight shift as a repo man. He was the only one in the office on that shift and he took a shot and went out, when his boss got in in the morning and couldnt find him, he checked the bathroom and couldnt get the door open, when he forced it he found him pushed up against the door when he went out. I still have guilt over that situation because they said he od'd around 1230 at night or so and he had called me around 12:20/12:30, so had i picked up the phone instead of saying "Im in bed ill call him back in the morning" i might have been able to get an ambo to his work before he died. But i didn't, so look out for each other, even if they're a stranger.