Laser drapes can be a useful safety device.
Ken Barat, Lawrence Berkeley National Laboratory
You may want to consider the use of laser curtains, made of fabric and usually hung from a ceiling track or similar system, as a way of containing laser beams.
There are several vendors of laser curtains, all with some proprietary technology involved and usually in the compostion of the surface exposed to the laser beams. Many contain a metal foil sandwiched between layers of fabric.
Where can laser curtains be useful in the photonics laboratory? One place is across a lab doorway, where there is either a temporarily disabled interlock or none at all. When the door is opened, a curtain can protect passersby not only from laser radiation but also from bright reflections and flashlamps. These may not be truly hazardous, but can disrupt normal activities outside the lab.
Carving out a “room within a room” is also useful. If you have a large laboratory room where the experiment occupies only part of the space, curtains around that space can eliminate the the need for everyone to wear eye protection. They can even reduce the necessity of laser safety training for those who never enter the protected area.
But when curtains partition off a portion of the room, there are several important issues that cannot be ignored: “How do I know if the laser is on?” “Is it safe to enter?” “How do I know the beam won’t escape?”
The first two questions can be addressed in several ways. The warning signs and lights that I’ve discussed in previous articles also can be effective with laser curtains. In practice, the “Yo, Adrian!” approach – yelling to a person on the other side of the curtain – often works. Not fail-safe, but adequate, and it will suffice in some situations.
The third question, that of preventing the beam from escaping, naturally requires that the curtains be hung carefully with enough overlap between them to avoid a gap from opening. But careful design of the entryway is also important. If it’s just a flap that you shove aside to enter or exit the laser area, the beam can escape. A dogleg entryway is one solution, where there is no straight line of sight between the protected and unprotected areas. Another solution is the air-lock approach, where you step through one flap and let it close behind you before you can open the next.
The laser curtain need not be floor to ceiling. It can start a foot or so above the floor and stop several feet short of the ceiling. Floor-to-ceiling curtains can interfere with air circulation and, perhaps more perilously, with the functioning of fire sprinklers in an emergency.
Yet another application of laser curtains is around a temporarily hazardous situation, like servicing a Class 1 laser on the factory floor. This introduces the possibility of carelessness, though, when people set the curtains up in a hurry and fail to position them properly.
There may be alternatives to laser curtains in some situations. The curtains are expensive and, for a semipermanent or permanent setup, it may be easier and cheaper to build a partition of sheetrock or similar material. Another alternative is nonlaser curtains such as those used around welders. These meet combustibility standards but are untested for their resistance to laser penetration. You must test them before putting them to use in your laboratory.
Meet the author
Ken Barat is the laser safety officer at Lawrence Berkeley National Laboratory in California; e-mail: [email protected].