I guess you want to hyperventilate because you want to beat your PB. I do not see any other reason why someone would want to do it. That's not the way to go. Hyperventilation won't help you to improve. Well, if you are a beginner, you will beat your PB easily with hyperventilation, but you will not learn anything, and there will be no training effect. Hyperventilation not only delays the urge to breath (which helps the beginners), but it strongly reduces the hypoxic tolerance (look up Bohr saturation curve), hence you will black out earlier. It increases the oxygen consumption (higher heart rate, peripheral vasodilatation), depletes myoglobin oxygen stores; strongly reduces cerebral blood flow (hence depleting oxygen stores in the brain too); it dissolves free calcium, and thus destabilizing neuronal fibers which causes tetanism, muscle tension and hence higher oxygen consumption again; and it also delays the onset of the diving response, hence again preventing the body going into oxygen saving mode. Put all together, and it is apparent that hyperventilation is very counterproductive, and its negative effects very quickly overweight the positive ones. Very carefully and precisely dosed hyperventilation can achieve some positive effects, but very most freedivers hyperventilate already naturally without realizing it due to stress (that's natural). Adding some hyperventilation voluntarily leads necessarily to performance degradation.
So if you ask whether hyperventilation before dry breath-holds is dangerous, then the answer is: there is no danger of drowning like at wet apnea, but the risk of blackout (and hence also some cerebral damage) is similar. There is always a risk of injury or choking when blacking out, so there is certain risk from this point of view too. However, the main reason for not doing it, is that it makes no sense and has no positive effect, and especially no training effect. Getting a new PB after a strong hyperventilation will even not help your self-confidence (if you need to impress yourself), because it is just a cheap way of cheating yourself.