It's all good,I've been Vaping kief in the 'box for many months and have had no problems at all. I don't even really clean it either,just brush the screen and carry on. I think that as long as nothing actualy melts into/through the screen you'll be fine. I've never tried the tray yet,no acess to oils. But if you would like a full evaluation by someone who is in no way qualified,send me some oil and I'll report back ASAP!