Thanks for those pointers.  I was unsure about shortening the classes to give time to clean.  Really helps that you think its a good idea.  Airing out the room is also very important for me.

Cynthia thanks for taking the time to read and comment.  I think it's more than reasonable with the climate we're in to shorten classes for cleaning/airing out.  It's for everyone's benefit right?  Take care.