Health & Safety
You must always bear in mind the hazardous effects that X-ray beams can have on your own body. If you have a clear understanding of the nature of X-rays, then safety rules will be much more logical.
X-rays are a highly-penetrating form of ionising radiation. Radiation is energy in the form of waves or particles. Radiation is all around us. Humans have been exposed to radiation from natural sources since the dawn of time. This radiation cannot be avoided. But radiation is also produced from a wide variety of artificial sources.
People in many occupations use radiation-producing equipment in the workplace. Some of these occupations include doctors, nurses, technologists, dental hygienists, pharmacists and security screeners.
Radiation is harmful to the human body in excessive doses because it can damage cells. The most important material in the human body is DNA – it contains all the information needed to produce the biological material for human cells and whole body. Ionizing radiation can damage human DNA. Cells can repair certain levels of cell damage. At low doses, such as that received every day from natural background radiation, cellular damage is rapidly repaired. At higher levels, cell death results. At extremely high doses, cells cannot be replaced quickly enough, and tissues fail to function.
Radiation effects can be categorised by when they appear:
- Prompt effects: effects, including radiation sickness and radiation burns, seen immediately after large doses of radiation delivered over short periods of time.
- Delayed effects: effects such as cancer induction that may appear months or years after a radiation exposure
Security X-ray machines generate radiation, but they do not pose health risks to operators or the general public if they are maintained and operated correctly.
Radiation doses are expressed in terms of energy deposited in the body. They can be measured in units called ‘Microsieverts’. During a baggage X-ray approximately 20 Microsieverts is applied to each bag. The outer surface of the X-ray machine is exposed to approximately 1 microsievert per hour. The insignificance of this dose is obvious when compared to flying on an airliner, which exposes a passenger to 5 microsieverts every hour. We receive approximately 2200 Microsieverts per year just from natural background radiation, from the sun, soil, etc. And just one medical X-ray incurs 20 Microsieverts. So the radiation exposure from security X-ray machines is EXTREMELY SMALL.
A common misunderstanding is that any exposure to radiation can contaminate a person. Exposure to radiation does NOT result in contamination. Radiation is a type of energy. Contamination can only occur if a person comes in direct contact with radioactive powder or liquid – in other words, a loose radioactive material. The radiation from X-ray machines is NOT radiation in any of these forms. Security x-ray machines only produce radiation when energised.
There have also been concerns raised about the safety of passing foods through security X-ray machines. Luggage X-ray machines do not make food radioactive in any way. (Interestingly, food passed through an X-ray machine at an airport is getting a lower dose of radiation than it will receive during the actual flight from natural radiation!)
The safety features commonly incorporated into baggage X-ray machines include:
- Perspex tunnels: Deters anyone from reaching inside the X-ray machine.
- Lead in rubber curtains: Prevents the X-rays from escaping at both ends Radiation is absorbed by these lead-rubber curtains at the entrance and exit ports.
- Lead casing: The sides of the conveyor or cabinet unit incorporate an appropriate thickness of lead shielding. This keeps the X-rays within the cabinet.
- Emergency stop (E-STOP) switch: This instantly cuts off the x-rays and stops the conveyer. Should be working at the entrance and exit ports of conveyer units and should be clearly labelled. One is also sometimes fitted on the control panel.
- Safety trip switches: Stops the belt and presents a message to the operator.
- Sinage: Warns of the presence of radiation and rules to follow. Sinage should always feature an ionising radiation warning symbol, the “trefoil”. The trefoil is the internationally recognised radiation warning symbol. The unit will be labelled with a sign carrying the words “Caution – This Equipment Produces X-Rays When Energised”. A sign should also be present above each of the openings, warning people not to place any part of the body inside the unit when the system is energised.
- Warning lights: Indicate that the unit is powered and show when X-rays are being generated.
Modern x-ray machines are so safe to operate because they use low-energy, pencil-thin beams of radiation that scan back-and-forth across a piece of baggage as it moves through the machine. Infrared beams installed within the equipment accurately start and stop the x-ray beam source so that the x-rays are not operational when there is not an item in imaging position.
Add to these features excellent shielding and it is easy to understand why they pose no health risk, if operated and maintained properly. If radiation risks are to remain low, personnel in every facility where baggage x-ray systems are installed must maintain strict adherence to all safety rules.
X-ray machines do produce high voltages and so must be considered potentially hazardous. Only properly trained technical staff should ever attempt to investigate or repair equipment, or remove panels.
Never operate an X-ray machine where it may be exposed to water, condensation or dampness.
Never place liquid containers on the X-ray unit. Closed liquid containers should only be screened once they have been put into appropriate plastic containers.
Do not operate an X-ray machine in a confined area, without adequate ventilation – as overheating of components will occur. Do not cover ventilation openings of the X-ray unit or the monitors. Never operate X-ray equipment in the presence of fumes or flammable gasses.
Never sit on the conveyor of an X-ray machine, even when the machine is switched off.
Keep hands away from the edges of the conveyor belt, end rollers, and any other moving parts of the X-ray machine.
Ensure that baggage does not pile up or stack inside or at the end of the inspection tunnel. Never operate equipment with worn connectors or frayed leads.
Never attempt to mend damaged leads with insulating tape. Never put coins, walkie-talkies or other metallic items onto the casings of x-ray machines. They can damage the equipment.
* The information about Health and Safety is provided here as a guidance only to compliment and not to replace procedures and guidelines used at your own locality/facility.