- Designing a Laser Lab: What to Do – and What Not to Do
Laser lab design can be tricky. Even when lab construction falls to a project manager, he/she often will rely on the laser user (many times a postdoc or grad student) and someone from the Environmental Health and Safety Division for design help. These folks are not always appreciative of each other’s needs and requirements. The postdoc, grad student or even a senior researcher has a firm image in mind of the experimental setup but can fail to consider institutional building codes; on the other hand, the EHS representative and construction manager are not aware of all the factors that affect laser work. The project manager’s chief concern is coming in under budget and then making the client happy. The user just wants to get to work.
A simple example of an unintended conflict is when the user selects the location of the optical tables but fails to consider the electrical panel clearance restrictions. Let’s highlight a number of design issues, starting with the exterior of the room.
On the exterior, my two pet peeves are location of the illuminated laser warning sign and door interlocks. For ease of installation, many signs are placed over the doorframe. This location is easily overlooked by staff walking down long hallways or around corners. The signs must be at eye level alongside the door. It would be ideal to place them on the door, but this will most often change the fire rating of the door, which must be considered. Remember, the purpose of the signs is to alert anyone who might wish to enter the laser room that the laser is on, or at least powered up. Positioning it out of sight above the door defeats its purpose.
The number of safety considerations involved in laser lab design can be mind-boggling. If the illuminated “laser in use” warning sign over the lab’s doorframe is too high, people entering the room might not see it.
Also, the ANSI standards Z136.1 and Z136.8 allow the use of card readers or electronic locks that are not slaved to the laser as a means of access control. With rare exceptions, few laser labs should need the traditional door interlock. Laser safety officers must involve users in getting beams contained and blocked. If open beams cannot be contained by perimeter guards, beam tubes, beam blocks and so on, then a barrier – e.g., a curtain – upon entry may be the solution, establishing a laser-free zone in the lab area. Of course, this does take up space, greater than the curtain’s interior physical space, just as the TARDIS (time and relative dimension in space) on Doctor Who.
Laser lab design guides can be useful but tend to deal only with the lab’s exterior. They cover items such as interlocks, warning signs, emergency shutoff, door hardware and hazard communication posting. Here are some interior considerations that might not appear in such a guide:
Eyewash shower placement is very important in a lab. All users must be able to access the station in an emergency.
Start with institutional code requirements – and recognize that most laser users have no real knowledge of these. You’ll have to do your research.
These requirements include clearance around electrical panels (National Electrical Code), although not all panels require clearance. If there is no button to push or switch to throw – just an electrical box on the wall, this does not need a 36-in. clearance space.
Another example is an eyewash shower, which requires more consideration than its small physical size might suggest. The following are standard rules for the eyewash shower: No obstructions, protrusions or sharp objects may be located within 16 in. of the center of the emergency shower facility’s spray pattern (i.e., a 32-in. clearance zone must be provided). No electrical apparatus, telephones, thermostats or power receptacles should be located within 6 feet of either side of the emergency shower or emergency eyewash facility. If receptacles are necessary within 6 feet, they should be equipped with ground fault interrupters. Emergency eyewash facilities and safety showers must be installed in unobstructed and accessible locations that require no more than 10 seconds for the injured person to reach along an unobstructed pathway. If both eyewash and shower are needed, they should be located so that both can be used at the same time by one person. Flooring under safety showers should be slip-resistant.
Depending upon the specific chemicals used in the lab, a flammable cabinet may be required. Pressurized gas cylinders and/or liquid nitrogen Dewar vessels will need storage space and storage devices in your floor plan. Biohazard hoods and radioactive materials storage – and the rules that go along with them – may also come into play. Do not forget requirements for oxygen deficiency detectors.
Other interior considerations
The next set of interior factors is a long list of real-world items. Here are just a few: The power consumption needs and outlet placement are never enough. As the user, you know how important temperature regulation is, but your project manager might not. This is not just the air temperature in the room, but also the contribution or heat load from chillers, pumps and other devices. Can they be pumped in from an adjoining room or space? What is the building’s history of water temperature as the day progresses or as seasons change?
A laser laboratory’s floor plan should account for walkways and standing space. In this lab, the laser table is so close to the counter that the user’s chair will not fit.
This next issue is so often missed, it’s criminal. The system that pumps in-room air right on top of your optical table can
be an unobserved problem until air currents and particulates start to affect laser experimental work. There is never sufficient space, so planning storage is critical to a well-run lab. Often, the solution to storage is shelves above the optical table. These can present two types of problems from interior design issues to human factor concerns: Shelf corners are great to hit your head on – and, if not planned correctly, can be too low, fighting equipment and chambers on the table for space. Planning also must go into how wires and cables will hang.
There also are a few human factors to consider. You and your staff must have sufficient walkway space around the lab and equipment. The minimum aisle clearance is 24 in.; main aisles used for emergency egress must have a clearance of 36 in., and a pathway clearance of 36 in. must be maintained at the face of any access/exit door.
As optical tables and lab shelves fill the room, remember that you must be able to reach these items. Can you reach optics that have to be moved? Does the work flow smoothly? Can you see monitors? Consider the use of stepstools, platforms and viewing angles. These days, you can and should consider remote viewing options, motorized mounts and automated items as real-world solutions.
Lab space should be physically separate from personal desk spaces, meeting areas and eating areas. This sounds nice, but at times, it can be nearly impossible to obtain. At the very least, sitting at a workstation should not put you or the other lab users at risk. Make sure that anyone at a workstation is protected from any direct or stray beams. No one should have to go through lab space where hazardous materials are used in order to exit from nonlab areas.
A funny thing happened on the way to the laser lab
In his decades of laser safety work, Ken Barat has seen his share of funny things. He shared two anecdotes with Photonics Spectra:
1. An electrician received a work order to wire up an illuminated laser warning sign for a new laser room, but when he arrived on the job site, no one was there. Seeing no obvious source of power for the sign – and unfamiliar with the fact that remote interlock connectors are a requirement of Class 4 lasers – he hung the sign and wired it into an isolated power supply. The user returned the next day to find the light installed and on ... with no way to turn it off. The wiring to the power supply was hidden inside the lab wall.
2. One laser lab had a typical red-mushroom-style emergency off button. But its location made it very likely that it would be pushed by accident, which, in fact, happened a few times. Someone in the lab decided to place a plastic guard over the button, but rather than using a flip-up type, screwed a plastic cover over the button, which meant that it could not be pushed. This solved the accidental-strike problem but made the button itself useless.
Air-handling systems can pump particulates onto workstations, which can affect laser experiments. In this lab, cardboard hung from the ceiling covers the air vents.
Padding on ceiling-hung shelving - here, the lab operators used pipe insulation - can help protect users' heads.
Padding on ceiling-hung shelving can help protect users' heads.
Floor space can be crowded in a laser lab, but tables should be positioned so that the power supply does not block the sink or other installations.
Air-handling systems can pump particulates onto workstations, which can affect laser experiments. In this lab, plastic draped from the ceiling blocks particulate interference by covering the air vents.
If room storage or shelving is installed too low, it could interfere with placement or use of lasers and other equipment.
If open beams cannot be contained by perimeter guards or other methods, then a barrier upon entry such as this curtain can establish a laser-free zone in the lab area.
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