Originally Posted by Blackcat31:
You would be meeting your state's minimum requirements for supervision but I personally would not leave a 5 yr old and a 1.5 yr old alone in any play area that I could not see directly into.
That age span is far too wide for my comfort.
However, as I've said you would not be breaking any licensing rules but it's definitely not ideal and not what I would consider best practice. (My 2 cents...) 
I agree here.
I would pull items the 1.5 yo could play with out of the playroom and allow the 5yo to play with intermittent checks, but I wouldn't leave the 1.5yo out of sight.