Risks of working with lasers
The directionality feature of laser beams makes them able to produce an extremely high power density (W/cm2). This feature, together with the laser beam’s specified wavelength (or several discrete and defined wavelengths), enables the laser beam to be focused into a small spot with the use of a lens. The power density, which is already high, can increase significantly.
The laser's ability to concentrate intense power levels into a tiny spot is the basis for laser uses in many fields of science. It also enables lasers to be used as a powerful cutting tool for metals, hard ceramic materials and even diamonds. However, the high power density raises safety concerns for the working environment where laser systems are used, since the nominal outputs of most laser systems are significantly higher than the threshold levels allowed for exposure to the eyes or skin.
Biological laser risks
Exposing eyes to a laser beam can often result in severe visual impairment, and contact with the skin can also result in a deep and painful burn. Therefore, it is important to know the potential damage that can be caused by a laser beam, and how these dangers are associated with different characteristics of the laser beam, such as wavelength, intensity, duration of exposure and more. Armed with such information, a scale of increasingly severe risks can be formulated. The specific wavelength of a given laser, together with its position on the risk scale, enables us to determine, with a fairly high degree of certainty, the protective measures needed to work safely with and around the particular laser equipment.
Momentary (or longer) exposure of any tissue to laser beams may result in actual injury caused by one or more of the following three potentially harmful mechanisms:
- Photothermal damage: The laser beam causes vibrations in molecules in biological tissue, thus creating heat in the tissue. The damage to the tissue ranges from alterations in protein properties (albumin) to burns, and tissue vaporizing until it carbonizes.
- Photo-acoustic damage: High power density results in high local temperatures, causing the fluids in the tissue cells to change their state and become gases, thus altering their volume and creating a mechanical shock wave that spreads to the adjacent cells and is liable to cause them to tear.
- Photochemical damage: Certain wavelengths in the UV spectrum and blue light in it cause reactions between organic molecules, or can destroy chemical connections in molecules. The effect is long lasting.
In practice, the dominant damage mechanism in each individual case depends on the characteristics of the laser beam and the characteristics of the tissue.
Physical risks of the laser
Fire and explosion: High-intensity lasers can cause flammable materials (fabric, paper, plastic, wood, etc.) to explode upon contact with flammable liquids and gases.
Risk of electrocution: Caused by the high input voltage for laser systems.
UV (non-ionizing) radiation risks: Radiation in this spectral field originates from flash lamps and continuous laser discharge tubes (CW), especially when using piping or mirrors to transfer UV radiation beams (such as quartz).
Risks of ionizing and non-ionizing radiation:
An excimer laser uses electronic gas discharge tubes (gas electron tubes) that operate with a high voltage between their electrodes. The voltage between the anode and cathode in the tube can be over 5 kilowatts and its operation can cause the following symptoms:
- Plasma creation (ionized gas aggregation mode)
- Emission of non-ionizing radio frequency (RF) radiation and electrical radiation (ELF)
- Emission of X-ray radiation.
Chemical risks of lasers
- Evaporation of toxic substances: The laser beam’s contact with chemicals can cause evaporation of toxic substances into the surrounding area.
- Chemical risks from the particular laser source:
- Color lasers containing toxic chemicals
- Lasers containing toxic gasses such as fluorine
- Leakage of the laser’s cooling liquids
- Risk of oxygen displacement when using lasers with inert gases (nitrogen, helium)