I suggest incorporating the inspection into a testing and training event - where someone has a go at using the equipment to check (a) they are able to use it correctly and (b) it functions correctly.  It's no use having the equipment if those who might be required to operate it aren't confident to do so, and there is nothing like a practical test to establish this.  

I am in agreement with Kate.  A visual inspection to ensure that they are undamaged and to ensure that they will perform as would be expected.  Then a evacuaton exercise, to see if they are fit for the job and can be used sucessfully to evacuate those that need them.  I assume that those that would need to use the sledge are in the minority and that the others are capable to evacuating themselves or with some assistance from the staff. 

Just two questions.  Have you considered moving those that are in need of the sledges to the ground floor, this may lead to a quicker response and may remove the need to this type of equipment,  and are you sure that you have enough staff in the quiet hours to carry out any evacuation.   

Thankyou all for your replies. They have been very helpful.