Ultraviolet index Exposure level Meaning Recommended protective measures
0-2 Level 1 Weakest Weather with weak ultraviolet radiation, no special protection is needed. If you are outdoors for a long time, it is recommended to apply sunscreen with SPF between 8-12
3-4 Grade 2 Weak The UV intensity is weak, it is recommended to apply sunscreen with SPF between 12-15 and PA+ before going out
5-6 Grade 3 Moderate The UV radiation is of medium intensity, it is recommended to apply SPF higher than 15 and PA+ before going out
5-6 Grade 3 Moderate The UV intensity is of medium intensity, it is recommended to apply SPF higher than 15 and PA+ before going out. It is recommended to apply SPF higher than 15, PA + sunscreen skin care products, wear a hat, sunglasses.
7-9 Grade 4 Strong UV radiation is strong, it is recommended to apply SPF20 or so, PA + + + sunscreen skin care products. Avoid exposure to sunlight from 10:00 to 14:00 hours.
10+ Level 5 Very Strong UV radiation is very strong, it is recommended to apply SPF 20 or more, PA + + + sunscreen skin care products, avoid exposure to sunlight.
Laser hazard and precaution
laser hazard and precaution
The harmful effects of laser devices on the human body and the working environment are called laser hazard, and the safety countermeasures taken against laser hazard are called laser protection. Hazards from laser devices can be broadly categorized into radiation hazards, electrical hazards, chemical hazards and mechanical hazards, usually only radiation hazards are considered.
Laser radiation can cause damage to the human eye and skin, with the former the most serious consequences. As the human eye on different wavelengths of laser transmission and absorption of different wavelengths of laser damage to the human eye parts are also different (see Figure [the human eye on the absorption of electromagnetic radiation schematic]). Eye injuries caused by laser radiation mainly include photogenic keratitis, corneal coagulation, carbonization and perforation, lens clouding, visual functional disorder "flash blindness", and retinal coagulation, hemorrhage and bursting. The main types of skin damage caused by laser radiation are hyperpigmentation, erythema and blisters. The extent of the damage depends on the size of the radiation dose, which is related to the output energy, working wavelength and working condition of the laser, of which energy is the most important factor. The human body and the working environment constitute a hazard not only direct light, but also reflected and diffuse light.
Laser processing and laser therapy, may produce harmful smoke, vapor and noise, etc., radiation hazards to the environment. High-power laser radiation can damage some precision instruments and even cause fire.
Protective measures against laser radiation are based on laser safety and protection standards. International standards are mainly the International Electrotechnical Commission (IEC) standards, the World Health Organization (WHO) standards, the International Organization for Standardization (ISO) standards and the International Radiation Protection Association (IRPA) standards. In addition, the American National Standards Institute (ANSI-Z-136) standards and the U.S. Bureau of Radiological Health (BRH) standards are commonly used.
All laser safety standards are divided into a number of safety levels for lasers according to parameters such as output energy, operating wavelength, and pulse width. The division is based on irradiation limits that are directly related to the damage threshold. Different standards of irradiation limit expression and value are not the same.
Laser protection is usually on the laser source, operators and the work environment to take appropriate protective measures. Specific methods are safety management, safety education, engineering protection, personal protection and medical supervision. ① safety management: the development of laser safety regulations, strict grading and labeling of laser products, to provide users with safe use guidelines. ② Safety education: safety education and training for personnel in contact with lasers. ③Engineering protection: Remove flammable substances and mirror reflectors on the laser light path, set up danger signs, and set up necessary alarm devices in the workplace. ④Personal protection: Equip personnel exposed to lasers with protective gear such as laser protective goggles. ⑤Medical supervision: conduct regular medical checkups for laser operators when necessary.
Laser safety and protection standards and measures
1 laser protection safety standards
1960 after the birth of lasers, 1963 on the basis of measured retinal and skin damage threshold, the maximum permissible exposure to lasers, followed by a wide variety of safety standards in the world of more than 20, 30 (of which the U.S. most of the safety standards). However, due to the different understanding of the operating threshold (is the microscope can check cell damage, is the inspection glasses can see the damage, or can be perceived as a decline in visual function), the damage threshold is based on the acute response or chronic response, the safety factor is to take the 10 or 1000, etc., so that the proposed safety standards vary greatly.
1.1 ANSI Laser Safety Committee
In order to use lasers safely, but also to reduce confusion, the American National Standards Institute (ANSI) set up the Laser Safety Committee, which organized a variety of forces, and, after research, published the ANSI "Safe Use of Lasers, Z-136, 1-1973". 136, 1-1973" safety standards.
In order to recommend reasonable and appropriate safety guidelines for the safe use of lasers with wavelengths of 0.2?m to 1mm, the committee categorized lasers into five groups based on whether the original laser beam was strong enough to cause damage to the eyes or skin; for example, Group I was unprotected because of its low power density and Group V had to be placed under the most stringent controls. This booklet discusses hazard evaluation and classification, control measures, laser safety programs, medical surveillance, other hazards, eye and skin exposure criteria, and laser parameter measurements.
Lasers are capable of injuring the eyes, skin, respiratory tract, central nervous system, and the entire body. Currently, safety standards are generally proposed only for the eyes and skin. Given that lasers are now used in machining, the potential for respiratory harm is growing, as is the potential for workers to be harmed by chronic laser exposure, it is important to take all five of these aspects of laser harm seriously.
1.2 Chinese laser safety standards
China has developed several standards for laser safety:
(1) GB7247-87 Radiation Safety of Laser Products, Classification of Equipment, Requirements and User's Guide. National Bureau of Standards issued on February 9, 1987, October 1, 1987 implementation.
(2) GB-10320-88 "Laser equipment and implementation of electrical safety". State Bureau of Technical Supervision December 30, 1988 release, January 1, 1990 implementation.
(3)GBl0435-89 "Workplace Laser Radiation Health Standards". Ministry of Health February 24, 1989 release, October 1, 1989 implementation.
(4) National Industry Standard JB / T5524-91 "Laboratory Laser Safety Rules". The Ministry of Machinery and Electronics Industry July 16, 1991 release, July 1, 1992 implementation.
2 laser protection measures
As mentioned earlier, the laser is dangerous, but as with electricity, as long as we do not paralyze and take it lightly, but strictly abide by the rules of safe operation, can be harmless to use the laser in the treatment. As all kinds of lasers have their own special attention, so in addition to the general safety rules, but also on the ultraviolet, visible, red and near-infrared, far-infrared and dye lasers, respectively, their eyes, skin and other injuries that may be caused by the protective measures that should be taken and safety standards, which will facilitate the laser workers on the use of lasers should be taken to take protective measures to do a number of things in mind, without having to This will make it easier for laser workers to take protective measures for the lasers they use, so that they have a clear idea and do not have to look ahead.
(1) the harm of far-infrared laser and its protection: commonly used carbon dioxide laser (10.6?m) all for the cornea to absorb, can not enter the eye. Because this laser is not visible and generally higher power, accidentally will burn the cornea, conjunctiva and eyelids. For corneal burns, the lightest is a small white cloudy spots, 10min after irradiation, only involves the corneal epithelium, not swelling, and then subside, no visible scar, the heavier is from the outside to the inside of the formation of cylindrical white spots, and then the heavier is the formation of ulcerated soup spots or perforation. Despite the severity, protection is fairly simple, requiring only a pair of flat glass glasses. The threshold value of carbon dioxide laser is 0.1W/cm2. carbon dioxide laser will be absorbed by the skin which is 0.2mm thick, and it can easily cause blistering or burning. Because of the higher power, it will burn at once, and the physiological response (such as pain) does not play a protective role. Transversely excited air pressure carbon dioxide laser can make air ionization. If 30mJ carbon dioxide is used to illuminate the skin on the surface of the forearm for 0.5 to 0.25s, the spot diameter is 10 ?m, and the irradiation stings and burns. Erythema appeared a few hours later, 24h later expansion, edema, and finally scarring. Protective measures wear work clothes and gloves.
(2) General protective measures: the laser should be closed up where possible. The laser beam should not leak except close to the target. The laser beam should not be at the same level as the eye. The laser beam should stop at non-reflective and fireproof materials. Pulsed lasers should have safety gates to prevent laser explosions. For each application, the lowest radiation level that will accomplish the purpose should be used.
The walls of the laser room should not be blackened, but should be painted with a light-colored, diffuse paint to minimize specular reflections and increase brightness. The room should be bright to minimize pupil size. It should also be well ventilated so that the concentration of xylene, carbon tetrachloride (for cleaning), nitrogen (for cooling), ozone, etc. in the air does not exceed the permitted value. Indoor furniture should be reduced to a minimum and surfaces of furniture should be rough. No uninvolved persons are allowed inside. Barriers should be set up so that people cannot approach the laser. A red light should be provided to indicate the operation of a high-power laser, as in the case of an X-ray machine. The laser should be operated from a distance, and the staff should be in the next room to operate the very high power.
All indoor personnel should wear appropriate protective glasses. Do not use a mirror for multiple purposes. Staff should wear overalls and gloves. To treat the laser like a gun, it is strictly prohibited to look directly at the laser beam, as far as possible away from the laser beam. Emphasize the operating rules of high voltage to prevent electric shock (more people are reported to be injured by electric shock than by laser in foreign countries). Regular eye examination. The first workers should strengthen the laser protection education.
3 laser safety and protection
3.1 Take appropriate measures: (1) Class A lasers emitted by the laser does not cause any biological hazards, can be exempted from taking control measures; (2) Class B lasers are a low-power range, the wavelength of 0.4 ~ 0.7?m, the power of less than 1mW, long-time staring may cause retinal damage, so we must take protective measures and use of the warning signs; (3) Class B laser is a low-power range, wavelength 0.4 ~ 0.7?m, the power of less than 1mW, long-time staring may cause retinal damage, so to take protective measures and use Warning signs; (3) Class C lasers are medium power range, people may cause biological damage by short time irradiation, so control measures are indispensable. This type of laser diffuse laser beam is not harmful; (4) Class D laser is a high-power range, can produce dangerous laser beam reflected laser beam, the human body short-term direct or diffuse exposure will cause biological damage, must take strict control measures.
3.2 Seriously implement the safe work system: (1) laser operation places, such as laboratories, treatment rooms should have a high degree of illumination, so that the staff pupil narrowing, reduce the amount of laser into the eyes. White or light-colored rough walls are used in the room to reduce the specular reflection surface. In the laser room or doorway, the laser beam is easy to reach the place set "laser danger" sign. (2) Laser staff pay attention to operating procedures: A, laser staff need to go through laser safety education and training; B, wear protective glasses, and pay attention to the selection of a variety of specifications; C, laser use that is the termination of the optical circuit, turn on the laser strictly comply with the operating procedures of water and electricity; D, contact with the laser staff can not be directly looking at the power or energy density exceeding the permissible threshold of the main beam, and regular physical examination; () the relevant units must be implemented. (3) The relevant units must implement laser safety protection measures, set up a safety monitoring system; (4) laser production unit of class B lasers must be in the panel of the conspicuous position of the "prohibit looking directly at the laser beam" warning signs and must be the protective cover. C, D laser must be closed with a closed cover to cover the entire laser, the installation of safety interlocks and key lock switch, the laser should be triggered before the warning signal, the panel of the conspicuous position of the police sign. Various types of lasers should also provide the wavelength range, maximum output energy and power, pulse width, repeat pulse frequency, beam divergence angle and other physical parameters.