For lasers aimed into the sky, there are four potential hazards. From most- to least-hazardous, they are:
- Eye hazard. The laser’s light is powerful enough that it could damage pilots’ eyes (as well as eyes of the aircrew and passengers). Eye damage can be caused by visible, infrared or ultraviolet laser light.
- Flashblindness hazard. The pilot is temporarily unable to see (like a camera flash) until the afterimage fades. Caused only by visible light.
- Glare and disruption hazard. The pilot cannot see past the light glare, until the light stops. Bright enough so the glare disrupts normal operations. Caused only by visible light.
- Distraction hazard. The pilot is distracted by the steady or flashing laser light. It is significantly brighter than other nighttime sources such as streetlights, runway lights, car headlights, etc. Caused only by visible light.
A 5 milliwatt laser: a distraction 2 miles away
The diagram below shows the hazard distances for a 5 milliwatt green laser pointer:
- It is a potential eye hazard from the pointer to about 52 feet.
- It is a temporary flashblindness hazard from the pointer, out to about 260 feet. On the diagram, this is illustrated in the inset photo “Near-flashblindness” which shows what a 5 mW laser looks like at 350 feet.
- It is causes glare and is a disruption hazard from about 260 feet to about 1,200 feet. This is shown in the “Glare” inset photo where the runway is not visible.
- It is a distraction hazard from the pointer to over two miles (11,700 feet). The distraction can be dangerous during a critical phase of flight, such as takeoffs and landings.
The laser’s light is not truly safe until it is indistinguishable from background lights on the ground. A pilot may notice a flashing dot of light, but it should not be enough to cause a distraction. (This does not mean that anyone should aim a 5 mW laser at a plane if it is over 2 miles away. For one thing, it is very difficult to gauge aircraft distances at night. Even more important, there simply is no reason to aim a laser at an aircraft except in an emergency situation such as a wilderness rescue.)
Click on the diagram for a larger version
For more info on the inset photos (cockpit views of laser light), see the “Effects on pilots” page
A 125 milliwatt laser: a distraction 11 miles away
More powerful lasers are hazardous at greater distances. The hazard increases as the square root of the power increase.
For example, a 125 mW laser is 25 times more powerful than a 5 mW laser. The square root of 25 (the power increase) is 5 (the hazard distance increase). Therefore, multiply the hazard distances for a 5 mW laser by 5, to find the hazard distances for a 125 mW laser. For example, if a 5 mW laser is an eye hazard out to 52 feet, a 125 mW laser is an eye hazard out to 5*52 or 164 feet.
The table below does the multiplications for you. It provides some sample laser powers and the corresponding hazard distances measured from the laser output. (Note that these distances are approximations. It is not as if a 5 mW laser is an eye hazard at 52 feet but is not an eye hazard at 53 feet. The distances give approximations where one hazard zone shades into another.)
Click on the table for a larger version showing additional data
How to be safe when using lasers at night
If you absolutely must point something out in the night sky (e.g., at a star party), use the laser to circle the object -- don’t aim directly at it. Additional suggestions are on the Tips for outdoor use page.