What's this "negative pressure" concept
Wordiology at work.
Think pressure differential for pressure hull work.
In the usual state, we have slightly higher absolute pressure inside compared to outside - giving lower cabin altitudes than the actual outside altitude. Structurally fine as round vessels work fine with hoop tension. Guarding against too much of a good thing, we have various pressure relief mechanisms so that the pressure differential doesn't get too high. We might refer to this situation as being a positive pressure differential.
Structurally, the reverse differential (higher absolute pressure outside) is not good due to structural instability. To guard against this there are various pressure relief mechanisms so that the pressure differential doesn't get too high. We might refer to this situation as being a negative pressure differential.
In both cases there is no negative pressure, per se - a bit hard conceptualising the air somehow sucking against the skin. The pressures in each space are quite normal and positive, if you like. However, the differential can either be trying to explode (positive diff) or implode (negative diff) the structure of the pressure vessel.
Typically we see the positive diff situation with gas bottles generally and aeroplanes - submarines are the usual example of negative diff structures.