A crawl space is a work place that is difficult to enter and hard to ventilate. It is tight, often dark and difficult to flee out of in case of an emergency.
The required size of a crawl space is:
In a crawl space of this size, you are allowed to work no longer than one and a half hours, followed by a 15-minute break. If a crawl space is smaller than this, you are allowed to work a maximum of one hour followed by a 15-minute break.