Avoiding anything big would probably be for the best anyway.

[And he didn't come fully unprepared! He's got gloves, hospital-type masks, and a couple long-sleeve coats for those who don't already wear long-sleeves.]

It's what I could come up with on short notice. If you come across any plants or gas clouds you can't avoid, these should protect you, at least temporarily. Try not to get stung by anything or breathe anything in, if you can.

The masks are only good for a couple hours before they need to be replaced, though, so only use them in an emergency.