If you check with the local aeromed service, or any other helicopter service, they should have a set of guidelines for emergency services. The one I'm most familiar with is almost identical to what Lewiston2Capt displayed. Our local service, Lifestar, flies a BK117. They require a minimum 60' x 60' LZ. We're required to warn them of hazards (powerlines, trees, towers, hazmat, etc). We may also be required to cover a landing of "Trooper 1" the state police Jet Ranger. They require 75'x75' during day and 100'x100' at night. Our landing zone marker is a simple ground strobe run off a battery pack. It's flat, about 3" tall, with a single amber strobe to mark the LZ. Our policy is to stage an engine, set up for foam operations by hoseline or master stream, about 100' outside that LZ. All vehicles, people, etc clear from the LZ, emergency lights and spot lights not to be directed on the LZ at night, as it affects the pilot's vision. If operating on the interstate highway, we close both directions of travel (the state police hate it when we do that...) We also assign a crew to assist the helicopter crew as needed with transfering the patient to the helicopter as directed by the chopper crew. Lifestar, here in CT, runs a safety program upon request. Check with the local service and see if they have a similar program. Hope this helps out.

Mike Jozwik
Farmington Vol. Fire Department