Safety experts and organizations are faced with laser-related non-beam hazards (NBH), such as electrical sparks, plasma radiation, and explosions, and other special safety regulations. The spread of laser technology has increased the number of non-beam hazards, and has made it easy for laser users to ignore these hazards.
????????Laser accident information can be found at Rockwell Laser Company (www.rli.com), which maintains a laser accident database (LID) that contains reports of more than 1,300 laser accidents in 40 years (see Table 1). LID classifies laser accidents into beams (eyes and skin) and non-beams (others). The results show:
??????(A) The number of non-beam incidents reported in the LID has exceeded the number of reported skin incidents.
??????(B) At present, more than 30% of all accidents can be characterized as NBH.
????????LID also reported that the two most common types of lasers in NBH accidents are Nd: YAG and CO2 (see Table 2). Unfortunately, not all laser types are verified and recorded in the LID, so the results may not fully reflect the facts. According to Rockwell's report, the number of NBH accidents was 67 in 1998, which is about 1/3 of the number of reported accidents each year. The increase in the number of NBH reports clearly supports the need to pay more attention to this hazard.
???????The American National Standards Institute (ANSI) Z136 series of standard specifications provides general information for identifying, evaluating, and controlling hazards of traditional beam hazards. However, the evaluation and control of NBH requires a completely different knowledge base than that of beam hazard identification, so laser safety experts may need to combine their experience with NBH to fully protect laser users.
???????Existing ANSI specifications
???????Part 7 of the ANSI Z136.l-2007 standard for the safe use of lasers defines NBH as 'hazards caused by direct contact with the laser beam through the human body.' The four main types covered by the current NBH definition include materials exposed to laser beams (eg, fire), exposed to laser system components (eg, capacitors), materials used to generate lasers (laser media such as dyes and gases), systems How to be used (eg machinery, limited space). Some specific NBH topics covered in the standard include electrical hazards, plasma radiation, waste lasers, explosions, manipulators, fires, and compressed gases. The standard states that some of these hazards will be life-threatening (electric shock). The place where the laser is used must ensure sufficient professional knowledge and protection to ensure timely and effective safety control of possible hazards. With the continuous advancement of laser technology, new requirements have been put forward for workplace safety, and laser safety experts will be eagerly waiting for the new theme of NBH.
????????Balance between beam and non-beam safety regulations
????????In the laser standard, how to balance the beam and non-beam problems is a challenge for laser users. In general, the standard attempts to explain the NBH problem by providing sufficient information to ensure people's alertness and adequate control methods, while not making the threat of NBH excessively affect users. However, this balance has difficulties in operation, because unlike the beam hazard, NBH causes all laser deaths and injuries and most laser serious injuries, so it also bears wider regulatory pressure, which is different. Eye and skin hazards caused by light beams.
????????Emerging NBH problems
????????It is predicted that in the next few years, NBH will receive more attention from laser safety experts with the emergence of new applications or the derivation of existing problems. Some of these new hazards are related to nanoparticle manufacturing, gas warning concerns, fire sources, and radiation sources. It has been shown that small-sized particles (<0.1 microns) are more dangerous to the human body than larger particles because of their higher activity. Although humans have been exposed to naturally-occurring nanoelectronic particles for a long time, man-made engineered nanoparticles will bring strong toxicity. The activity of a material depends largely on the size of its surface area, which varies according to the particle radius, and the volume depends on the cube of the radius. Therefore, nanoparticles have a higher surface area / volume ratio and higher activity than large particles of the same material. This increased activity has a profound effect on respiratory effects, blood / brain blood vessel walls, and fire / explosion hazards. Finally, when nanoparticles can easily enter the deepest region of the lungs (unlike larger particles just staying in the upper respiratory tract), they may also enter all parts of the body with their tiny size.
????????Potential flammability hazards of low-power lasers. Section 7.2.3 of the ANSI ZI36.I-2007 standard recommends that enclosing a Class 4 laser beam will cause a fire hazard, especially when the material is exposed to an environment where the beam irradiation is greater than 10 W / cm2 Down, or when the beam power exceeds 500mW. The National Fire Protection Association mentioned in the NFPA laser fire protection standard that laser beams greater than 0.5W / cm2 should be regarded as flammable.
????????Generation of ionizing radiation Section 220.127.116.11 of the ANSI Zl36.l-2007 standard briefly mentions the possibility of ionizing radiation as a laser by-product, but does not provide clear guidance for identifying or controlling hazards. X-rays can be generated when high voltages (greater than 15kV) are applied to vacuum tubes (used in rectifiers, thyristors, and power supplies) or discharges are applied to lasers. Such facilities are usually fully protected by manufacturers. Free electron lasers have higher ion radiation problems, including X-rays, neutrons (10MeV or higher), mesons (> 1GeV electron beam), synchrotron radiation (electron beam bending at the photon fan) and attenuated radiation of excitation products .
???????The concealment of laser beam accidents has always existed, and is particularly obvious to NBH. More accident data is maintained by various government agencies, but it does not indicate whether NBH occurred during the use of the laser. At present, there are some situations where NBH accidents are often reported as caused by industrial cleaning problems, rather than related to the laser itself.