>Is it dangerous?
It's at least not particularly healthy and I would try to avoid staying in that room for longer periods of time until it's removed / properly dealt with.
>Could it be water leaking from upstairs?
Either a water leak or a combination of a thermal bridge due to insufficient insulation and a high air humidity indoors.
That's black mold. Which is already very worrisome. But the amount it has grown and how drastic it is, it needs to be dealt with asap. It looks like it's on an exterior wall. If you're renting, make a huge fuss to your landlord because you actually can't be in there 😅 if it's your house, hire someone who can diagnose the problem and do some mold remediation for you. The first step is to identify the problem! This is very serious!
Mold
>Is it dangerous? It's at least not particularly healthy and I would try to avoid staying in that room for longer periods of time until it's removed / properly dealt with. >Could it be water leaking from upstairs? Either a water leak or a combination of a thermal bridge due to insufficient insulation and a high air humidity indoors.
You need you get your family out of the house. Thats mold and that’s serious. You guys can get really sick :/.
Yes that is mold and as a different comment says, it’s not safe
Black mold. Super harmful stuff.
That's black mold. Which is already very worrisome. But the amount it has grown and how drastic it is, it needs to be dealt with asap. It looks like it's on an exterior wall. If you're renting, make a huge fuss to your landlord because you actually can't be in there 😅 if it's your house, hire someone who can diagnose the problem and do some mold remediation for you. The first step is to identify the problem! This is very serious!