The ADS works by firing a high-powered beam of 95 GHz waves at a target, which corresponds to a wavelength of 3.2 mm. The ADS millimeter wave energy works on a similar principle as a microwave oven, exciting the water and fat molecules in the skin, and instantly heating them via dielectric heating. One significant difference is that a microwave oven uses the much lower frequency (and longer wavelength) of 2.45 GHz. The short millimeter waves used in ADS only penetrate the top layers of skin, with most of the energy being absorbed within 0.4 mm (1/64"), whereas microwaves will penetrate into human tissue about 17 mm (0.67").[

The ADS's repel effect in humans occurs at slightly higher than 44 °C (111 °F), though first-degree burns occur at about 51 °C (124 °F), and second-degree burns occur at about 58 °C (136 °F). In testing, pea-sized blisters have been observed in less than 0.1% of ADS exposures, indicating that second degree surface burns have been caused by the device. The radiation burns caused are similar to microwave burns, but only on the skin surface due to the decreased penetration of shorter millimeter waves. The surface temperature of a target will continue to rise so long as the beam is applied, at a rate dictated by the target's material and distance from the transmitter, along with the beam's frequency and power level set by the operator. Most human test subjects reached their pain threshold within 3 seconds, and none could endure more than 5 seconds.

Like all focused energy, the beam will irradiate all matter in the targeted area, including everything beyond/behind it that is not shielded, with no possible discrimination between individuals, objects or materials. Anyone incapable of leaving the target area (e.g., physically handicapped, infants, incapacitated, trapped, etc.) would continue to receive radiation until the operator turned off the beam. Reflective materials such as aluminium cooking foil should reflect this radiation and could be used to make clothing that would be protective against this radiation.

Many human tests have been performed on over 700 volunteers and including over 10,000 exposures by ADS. A Penn State Human Effects Advisory Panel (HEAP) concluded that ADS is a non-lethal weapon that has a high probability of effectiveness with a low probability of injury:

no significant effects for wearers of contact lenses or other eyewear (including night vision goggles)
normal skin applications, such as cosmetics, have little effect on ADSʼs interaction with skin
no age-related differences in response to ADS exposures
no effect on the male reproduction system
the limit of damage was the occurrence of pea-sized blisters in less than 0.1% of the exposures (6 of 10,000 exposures).
In April 2007, one airman in an ADS test was overdosed and received second-degree burns on both legs, and was treated in a hospital for two days. There was also one laboratory accident in 1999 that resulted in a small second-degree burn.

Possible long-term effects
Many possible long-term effects have been studied, with the conclusion that no long-term effects are likely at the exposure levels studied. However, overexposures of either operators or targets may cause long-term damage including cancer. According to an official military assessment, "In the event of an overexposure to a power density sufficient to produce thermal injury, there is an extremely low probability that scars derived from such injury might later become cancerous. Proper wound management further decreases this probability, as well as the probability of hypertrophic scarring or keloid formation."

Cancer: A mouse cancer study was performed at two energy levels and exposures with a 94 GHz transmitter: a single 10 second, 1 W/cm2 exposure; and repeated 10 second exposures over 2 week period at 333 mW/cm2. At both energy levels, no increase in skin cancers were observed. No studies of higher energy levels, or longer exposure times have been performed on millimeter wave systems.
Cornea damage: tests on non-human primate eyes have observed no short-term or long-term damage as the blink reflex protects the eye from damage within 0.25 seconds.
Birth defects: millimeter waves only penetrate 0.4 mm (1/64") into the skin, making direct damage to the testes or ovaries impossible.
Blisters and scarring: pea-sized blistering due to second degree burns occurred in a very small minority (less than 0.1%) of tested exposures, which have a remote potential for scarring.
ADS operators would be exposed to more than the standard maximum permissible exposure (MPE) limits for RF energy, and military use requires an exception to these exposure limits.