types of equipment should have appropriate training to minimize the risk of their being exposed to harmful ionizing radiation.

6.C.7.4 Miscellaneous Physical Hazards Presented by Electrically Powered Equipment
Magnetic Fields

If an object moves into the attractive field of a strong magnet, it can become a projectile when it is pulled rapidly toward the magnet. Therefore, objects ranging from keys, scissors, knives, wrenches, and other tools to oxygen cylinders, buffing machines, and wheelchairs and other ferromagnetic objects must be excluded from the immediate vicinity of the magnet, for the sake of both safety and data quality, in the case of NMR.

Even relatively small peripheral magnetic fields can adversely affect credit cards, computer disks, and other magnetic objects, as summarized in Table 6.1. It is prudent to post warnings at the 5-gauss (G) line and to limit access to areas with more than 10 to 20 G to knowledgeable staff. People wearing heart pacemakers and other electronic or electromagnetic prosthetic devices should be kept away from strong electromagnetic sources.

Superconducting magnets use liquid nitrogen and liquid helium coolants. Thus, the precautions associated with the use of cryogenic liquids must be observed as well. (Also see section 6.E.2.)

Rotating Equipment and Moving Parts

Injuries can result from bodily contact with rotating or moving objects, including mechanical equipment, parts, and devices. The risk of injury can be reduced through improved engineering, good housekeeping, and safe work practice and personal behavior. Laboratory workers must know how to shut down equipment in the event of an emergency; must enclose or shield hazardous parts, such as belts, chains, gears, and pulleys, with appropriate guards; and must not wear loose clothing, jewelry, or unrestrained long hair around machinery.

Cutting and Puncturing Tools

Hand injuries are probably the most frequently encountered injuries in laboratories. Many of these injuries can be prevented by keeping all cutting and puncturing devices fully protected, avoiding the use of razor blades as cutting tools, and using utility knives that have a spring-loaded guard that covers the blade. Razor blades, needles, and other sharp objects or instruments should be disposed of carefully rather than simply thrown into the trash bin unprotected.

Glass cuts can be minimized by use of correct procedures (for example, that for inserting glass tubing into rubber stoppers and tubing, which is taught in introductory laboratories), through appropriate use of protective equipment, and by careful attention to manipulation.

Noise Extremes

Any laboratory operation that produces significant noise (85 decibels or greater) needs a hearing conservation program to protect employees from excessive exposure, that is, exposure to significant noise for an 8-hour average duration. An audiologist or industrial hygienist should be consulted to determine the need for such a program and to provide assistance in developing one.

Slips, Trips, and Falls

The risks of slips, trips, falls, and collisions between persons and objects can be reduced by cleaning up

TABLE 6.1 Summary of Magnetic Field Effects


Level at Which Effects Occur (gauss)

Effects on electron microscopes


Disturbance of color computer displays


Disturbance of monochrome computer displays


Erasure of credit card and bank card coding


Effects on watches and micromechanical devices


Lowest known field effect on pacemakers


Saturation of transformers and amplifiers


Erasure of floppy disks



SOURCE: Adapted from Site Planning Guide for Superconducting NMR Systems, Bruker Instruments (1992).

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