All amateur stations, regardless of power, must comply with the requirements for RF radiation exposure spelled out in Part 97. The licensee of the amateur station is responsible for ensuring that an amateur station complies with FCC Rules about RF radiation exposure.
An Amateur Radio operator demonstrate that he or she has read and understood the FCC rules about RF-radiation exposure by indicating his or her understanding of this requirement on an amateur license application form at the time of application.
Exposure limits vary with frequency because the body's ability to absorb RF energy varies with frequency.
To determine compliance with the maximum permitted exposure (MPE) levels, safe exposure levels for RF energy are averaged for a "controlled" RF environment over a time period of 6 minutes.
A factor you must consider if your repeater station antenna will be located at a site that is occupied by antennas for transmitters in other services, is that your radiated signal must be considered as part of the total RF radiation from the site when determining RF radiation exposure levels.
From an RF safety standpoint, the duty cycle affects the minimum safe distance separating an antenna and the neighboring environment since: