Control measures for biological effects of RF Radiation

Protective measures

The purposes of reviewing this hazard is look at the effects of exposure to RF fields and assess its possible impact in human health. Such an assessment is necessary for the limiting exposure to RF during the testing of a gunn diode.

Protective measures include engineering controls, administrative controls, and personal protection. Where surveys of RF fields indicate levels of exposure in the workplace in excess of limits recommended for the general population, workplace surveillance should be conducted. Where surveys of RF fields in the workplace indicate levels of exposure in excess of recommended limits, action should be taken to protect personnel.

Engineering controls

Engineering controls should be applied, where possible, to reduce emissions to acceptable levels. Such controls include good safety design and, where necessary, the use of interlocks or similar protection devices.

For this experiment the supply should always be isolated when making alterations.

Administrative controls

Administrative controls that can be used to reduce or prevent exposure to RF fields are:

Access restriction, e.g., barrier fences, locked doors.
Occupancy restriction (only to authorized personnel).
Warning signs, and visible and audible alarms.

For this experiment access restrictions are over the top, but allowing only the people involved in the experiment around the test area can be implemented, and warning signs indicatingthe 'High RF areas' can be used.

Personal Protection

Protective clothing, such as conductive suits, gloves, and safety shoes, can be used. Their use should be confined to ensuring compliance with exposure standards, when engineering and administrative controls are insufficient to do so. Safety glasses have also been proposed for RF protection, but there is no convincing evidence that any of them are effective. The use of personal protection (protective clothing), though useful under certain circumstances, should be regarded as a last resort to ensure the safety of the student.

Wherever possible, priority should be given to engineering and administrative controls. Where personnel could be expected to incur exposures in excess of the limits applicable, consideration should be given to providing appropriate medical surveillance.

Note: The NRPB suggest a limit of 0.4W/kg of body weight for radiation within the body. More stringent standards are applied and a level of 100W/m².

Calculating the maximum working 'safe' distance

It must be noted that the results are referring to the eye, and under no circumstances should you look down a waveguide which is being operated.

Limit for eye: 100mW/10g.
Conversion: 100mW/m²=10mw/cm².

Calculating the value of absorption (W/m²)

$Absroption equation$

S - Expected value of absorption (W/m²)
G - Gain
P - Receiving an input power
r - Radius distance (m)
PG - ERP (effective radiated power)

Substituting the values

$Attenuation by distance diagram$

Therefore, the maximum safe working distance is 2.82m.

Actions to followed

Isolate supply when making alterations or not in use.
Authorized personnel in the test area only.
Signs indicating 'High RF areas'.
Follow the safe distance limits calculated.
Care taken not to look directly down the waveguide output.