Question for Q400 crew

[grow45]

I've been doing a fair bit of flying with FlyBe on the Q400 recently but have only just realised that the safety brief does not include use of oxygen masks. Presumably this is because at a cruise of 23,000ft you can get below 10,000ft in a a very short time so they are deemed not to be needed but would be interested to have this confirmed.

Also what would the max rate of descent used in such an situation be.

Thanks

g45