Jane,

Not quite sure what you mean by a batting cage..i.e. does it have a ball machine?

I am thinking that it is enclosed and that is the issue.  We have had some similar issues with tennis courts that are fenced and only have one entrance/exit and have had some trouble with entrapment.

Our recommendations now are to ensure there are adequate ways to get out if needed even though you might have to chase a ball now and then.  We also have this issue with our permanent hockey rinks.  These rinks are built in just about every school ground in town and often only have one entry/exit.  We are recommending additional ones to ensure the rink does not become an entrapment area.