Better safe than sorry .
neighbor behind my current house had friends down for the weekend JUly 4th last year. On their way out of the house , one of the cousins (whatever) flips his smoke b ut t off the porch into the bark/mulch . It smoldered and eventually the porch /decking started to burn. Everybody including me and the other houses had went down to the beach to enjoy the day.
across the street is a very nosey neighbor , but a nice guy, and he was the only one to see around to notice the gathering smoke. He went over to investigate , and found the front porch in falmes from underneath.
I would have called the fire dept....but That might have been too late... he saw the water hose hooked up and laying near by , we have alot of pressure. So he was able to put the fire out and control it . The damage was limited to the deck , but could have burnt the house down had the neighbor not noticed the smoke, after all there are alot of cook outs and on the4th of July . He was nosey and daring and it paid off.
My house might have been in danger had this house been in full flames.
The family is still giving him money and presents all the time for his help.
I don't think this is the best way of looking at it.
In this case it was cool, because the guy didn't go inside the house, he looked around outside, and saw the fire. I don't think the vast majority of people are too offended by somebody coming onto their lawn. Inside their house is a completely different story though.
And the "better safe than sorry" mentality is just too ambiguous as you can apply it to anything.
I hear the smoke detector going off at your house:
Should I knock on the door? Well you could be passed out, and waiting a minute to see if anybody comes could be the difference between life and death or a serious amount of damage. Better safe than sorry.
Should I try to call you? Well the time it would take for me to get my phone and dial your number and let it ring 6 to 10 times could be the difference between life and death, better safe than sorry.
Should I call the authorities? Well the time it would take for them to get here could be the difference between life and death, better safe than sorry.
So some could argue anything short of barging in at the first appearance of something wrong is being better safe than sorry. That doesn't really fly with me.
If you see something that could be wrong:
1. Reasonably investigate (call, knock on the door, listening, smelling, look around).
2. Unless you observe something unquestionably serious (hearing cries for help, see flames, etc.) call the authorities and wait. A smoke detector going off, no human response, dog barking, or any other minor irregularity isn't enough.
I would probably be upset if someone barged into my house and nothing was wrong. I'm not gonna sue you, but it would probably strain our relationship and I'd expect you to pay for a new lock/window/door however you forced your way into my house. (Though at the same time, I'd be grateful if you barged in and saved me

) The thing is 99.9% of the time it's going to be nothing, and that .1% when it is something 99% of the time it would be better to wait for the authorities.
(This assumes you're not close with the person, if you're close with the person it's different, but that's because it's not really barging in/trespassing.)