I don't know about the distance, but once I lit a stick of incense, and I forgot to move the orchid that was right next to it. The smoke was going over the blooms. The next day, all the blooms wilted and fell off. I don't know how far away you have to put an orchid though. I do burn incense regularily in the same room, and have not seen any ill effects. Then again I only leave it lit 5 minutes, or else the smell is too strong for me.
__________________ Camille
Completely orchid obsessed and loving every minute of it....
I regularly light incense in my orchid room (er, that's another name for my living room) and don't have problems. But I also cut it short after a few minutes.
I occasionaly lit a stick in my living room and leave it burn until it is completely used up, though I have no problem with my orchids which are approximately 2 mt. distant.
My living room is also my orchid room, and my bedroom, and study, and wherever there is a window. I regularly light incense , and am also a smoker. (I know, I know!) As long as there is fairly good circulation, everything should be fine. I've never seen any ill effects on my plants.