Although you may not realize it, you will also have to know and abide by the safety regulations posed by various agencies when designing and implementing an RFID system. There are three main groups of safety concerns. First is the safety of personnel when installing and working with equipment, especially electrical equipment. Second is human exposure to radio frequency and electromagnetic fields (also commonly called electromagnetic radiation, or EMR). Third is the safety of other equipment or products when exposed to EMR.
When designing and installing an RFID system, you must make sure that not only is your equipment safe and protected from damage, but also, more importantly, that your or your customer's personnel have a safe working environment.
Although you may love your interrogators to death, always remember that personnel safety is the main priority!
There are many organizations publishing safety laws, recommendations, and best practices. In the United States, the organization ensuring the safety and health of workers is the Occupational Safety and Health Administration (OSHA) under the U.S. Department of Labor. Every warehouse, plant, or company has its own safety manager or officer, who is responsible for its safe working environment. However, it does not mean that you are not also responsible! You must make sure that you know the OSHA safety regulations related to any facility where you are implementing your system and that your employees or contractors have gone through the OSHA or other required safety training.
There are a few things that you need to watch for:
You cannot install or leave any equipment in a place where it could obstruct the access to any safety equipment, such as fire extinguishers, drinking fountains, or fans, or block access to exit doors.
Make sure that your equipment, mounting, and cables do not cause a trip hazard.
When installing equipment far from the ground (for instance, by the warehouse ceiling) you must use a ladder, a scissor lift, and/or a safety harness to prevent falling.
When installing electrical equipment, do not forget proper grounding and safety practices published by the U.S. National Electrical Manufacturers Association (NEMA).
For electrical work such as running electrical lines or adding additional circuits, I recommend hiring a certified electrician, or if possible use the facility's electrician. It is always a good idea to cooperate with the technicians or electricians who are employed or contracted by the facility, because they already know the space and possible issues as well as regulations they have to comply with.
NEMA also provides ratings of enclosures. These ratings determine the use of the NEMA enclosure, and how much protection it provides and what conditions it can withstand. You will need to use NEMA enclosures when installing interrogators in order to protect them from extreme temperatures, liquids, humidity, and other conditions.
When working with electrical equipment and electricity in general, you should know the standards published by the U.S. National Fire Protection Association (NFPA), which develops fire, electrical, and building safety codes. The NFPA's standards include the National Electrical Code (NEC), which describes specifications for electrical equipment and parts, as well as markings for hazardous products (NEC 500 and NEC 505). Other markings you may see on electrical products include UL or ULC. UL stands for Underwriters Laboratories (C for Canada), and this mark signifies that the product or device has been tested and approved by this organization and it is safe to use. In Europe, you may see the CE mark, which is the equivalent to the U.S. UL mark.
To learn about safety requirements outside the United States, you may want to check with the European Agency for Safety and Health at Work, which is the European equivalent of OSHA; the International Commission on Occupational Health (ICOH); the International Labour Organization (ILO); and the World Health Organization (WHO).
Because exposure to radiation can be harmful to humans, there are regulations that set limits on the allowable amount of human exposure to radiation from various sources, including radiation from electromagnetic fields.
The International Commission on Non-ionizing Radiation Protection (ICNIRP), which is allied with the WHO, publishes guidelines for human exposure to electromagnetic fields. Its guidelines were adopted by the EU and some world administrations.
ICNIRP specifies that low frequencies under 10 MHz can have effects on the central nervous system because of electric current flow in the human body. The exposure to low frequencies cannot be time-averaged. Frequencies above 100 kHz, on the other hand, can have a warming effect on the human body. (You do know how the microwave oven works, right?) Exposure to high frequencies can be time-averaged. However, do not get too worried. These effects are related to strong magnetic and electric fields and high radiated power.
The U.S. military specifies (complying with ANSI/IEEE) that the safe dosimetric parameter for exposure to RF fields is 0.4 watts per kilogram (W/kg) for controlled exposure and 0.08 W/kg for uncontrolled exposure. This ensures at least a safety factor of 10 below the body-specific absorption rate, which is 4 W/kg.
Let's say that you weigh 90 kg (200 pounds). Your safe uncontrolled exposure could be up to 7.2 watts (90 kg × 0.08 W/kg = 7.2 W). You know that the maximum allowed radiated power from RFID systems in the United States is 4 watts, which is the power you would be exposed to if you stood right in front of the antenna. (If you weighed at least 50 kg, which is about 110 pounds, you would still be safe.)
The FCC publishes exposure limits in its Section 1.1310 that are based on the guidelines of the National Council on Radiation Protection and Measurements (NCRP) and ANSI. The limits are divided into limits for occupational and therefore controlled exposure, and limits for the general public, which means uncontrolled exposure. Generally, the recommended safe distance from RFID antennas emitting allowed EIRP for prolonged periods of time is 9 inches (about 27 cm).
When working with hazardous materials or explosives, you have to follow an extra set of rules. The military has always led in the development of such standards, and currently follows the Hazards of Electromagnetic Radiation to Ordnance (HERO) and Hazards of Electromagnetic Radiation to Fuel (HERF) standards.
HERO specifies the measures of electro-explosive devices' (EEDs) susceptibility:
Maximum no-fire current (MNFC), which is measured in milliamperes (mA). MNFC is the largest current that can be induced in the EED and does not initiate a detonation.
Maximum no-fire power (MNFP), which is measured in milliwatts (mW). MNFP is the highest power that can be absorbed by the EED without detonation.
HERO specifies three categories of EEDs:
HERO Safe Such a device cannot be initiated by electromagnetic radiation, and no protection is necessary.
HERO Susceptible Such a device could potentially be initiated by electromagnetic radiation. The sensitivity of this device is no less than 2.25 W MNFP and 340 mA MNFC.
HERO Unsafe The device has to be considered Unsafe if the environment cannot be sufficiently analyzed and the device cannot be determined HERO Safe or Susceptible. Protective measures for the worst possible scenario have to be taken. A device is also considered Unsafe if it withstands less than 2.25W MNFP and 340 mA MNFC, with the worst-case susceptibility of 85 mA MNFC and 54 mW MNFP.
If you are using active tags to tag explosives or EEDs, you should use a tag with maximum transmitted power under 54 mW, or 0.5 W to be on the safe side.