Can't you just dust a little ricin around the place?
Or do you have to spray it somehow?
( Mr. Tea 'ulmmm'/'mmneurgh', Thu 7 Jul 2005, 13:36, archived)

Just been reading up on it here
www.bt.cdc.gov/agent/ricin/facts.asp

Looks like you're right but I should imagine that without it being injected it would be about as effective as the Anthrax letters - ie not very
( Fenris temporary Lazarus, Thu 7 Jul 2005, 13:41, archived)