RFSigns Envelope Method™
A POSITIVE ENVELOPE is an enclosure secured from access. Positive Envelopes ensure the public can't get into over-exposure areas. They also ensure that only employees with authority (and training) have access to occupational overexposure areas and danger areas.
A PASSIVE ENVELOPE is an enclosure that is not locked or is a marked-off area (rope, tape, paint, signposts, etc.) beyond which personnel should not go without first employing safety controls. Passive Envelopes are not normally suitable for controlling public exposure. Passive Envelopes are suitable barriers for trained, authorized personnel, following procedures, as long as the Passive Envelope is within a larger Positive Envelope.
The Envelope Method is an approach created by RFSigns.com to help visualize safety zones ("envelopes") that should be marked with RFSigns.