Most non-military laser use is indoors. Over the years, this has resulted in the development of procedures for safe use of even the most powerful lasers. Sufficient means are available for shielding laser beams and control of access to the laser area. Thus, these lasers can be used with minimal risk.
In military applications, most use of lasers is outdoors and exposure to the laser beam cannot physically be prevented. Often, low power modes are available for training purposes. For the rest, powerful lasers are dealt with as if they are weapons. The risk of exposure is reduced by operating procedures, training and discipline.
Non-military outdoor use of high powered lasers, i.e. of Classes 3B and 4, mostly occurred in a relatively professional and controlled setting, e.g. in atmospheric research or at artistic laser displays. However, over the years, access to powerful laser pointers has become quite easy for the general public. The purchase and use of even the highest class of lasers may be perfectly legal. In the Netherlands, for instance, it is not allowed for retailers to sell Class 3R, 3B and 4 lasers to civilians, but possession and use thereof is legal. Thus, the use of powerful lasers now is more widespread and people that have no training are using them in an uncontrolled environment, sometimes with the intend to harm or hamper.
A new risk is developing; powerful lasers for repelling birds or other animals away from airports or agricultural fields. In some cases, these lasers will also be used by professionals, in a setting where safety measures are in place and the public will not easily be exposed, such as airports and off-shore helicopter platforms. In other cases, these bird repelling lasers will be used by poorly or not trained persons, not restricted by operating procedures, and at places that are easy accessible for the public. The associated risks are substantially greater than those for high powered laser pointers, as the bird repelling lasers do not only have high power, they have low divergence as well. The effect is that these lasers have hazard distances of kilometres, rather than tens or hundreds of metres, as will be explained in this paper.