Wise precaution, Verne.
BTW, Here is a link to a site that has the % concentration of Sodium Hydroxide in various items. It's so nice to see that Crest Tooth Whitening Strips have the same ingredient of Sodium Hydroxide as Purple Stuff and Drano. Though the powdered Drano ranges from 30% to 60% Sodium Hydroxide and the purple stuff is only 1% to 5% concentration.
http://hpd.nlm.nih.gov/cgi-bin/house...chem&id=19