Design Specifications for Class IV Laser Laboratories
This summary of NC State design guidelines for Class IV laser laboratories provides additional detail for design and construction to meet the basic requirements set forth in the latest edition of ANSI Z136.1, American National Standard for Safe Use of Lasers.
The final design for Class IV laser laboratories at NC State University will be determined through a review of proposed laser usage involving the responsible principal investigator (PI) and the NC State Laser Safety Officer (LSO), who resides in the NC State Environmental Health and Safety Center. The LSO will need to approve final design.
In some cases, laser lab design determined by the LSO and PI will deviate from this specification to achieve the best mix of safety and flexibility / efficiency for the principal investigator. For this reason, it is strongly recommended that laser design discussions be held early in the design process with participation from both the principal investigator and NC State laser safety officer (LSO).
Please contact the NC State LSO for any questions regarding this specification.
Entryways into the laser usage area shall have signs that alert personnel to the type(s) of laser(s), wavelength(s) in use, and maximum power level(s) that may be encountered within that particular lab. A list of authorized users and emergency contact numbers should also be provided on this sign. This is typically a laminated sheet attached to the door. A person entering the lab will use the posted information in selecting appropriate laser eye wear (goggles) before passing into the laser usage area. See "goggle station" in section V, Laboratory Layout
In addition, an ANSI compliant illuminated laser warning sign shall be mounted above the entryway to the lab and shall be illuminated whenever the laser is energized and capable of producing a beam. This sign contains the following warning:
Please contact the NC State Laser Safety Officer for preferred equipment.
The door to the laboratory shall be equipped with a self-closing device and be secured at all times. The door may be locked with a standard keyed lock, but a cipher lock with key override is preferred so that the code may be easily changed as necessary. Key override is provided for custodial services or emergency access. See photo example.containment curtain shall be hung on a track with rollers which, when closed, fully protects the doorway from stray beams that might otherwise be reflected out the door. The curtain attaches to the walls by a Velcro strip. The curtain material shall be capable of stopping laser radiation from the ultraviolet to the infrared and comply with ANSI: Z136.1- Section 7.5. A overlap of ~ 12 inches of two vertical curtain pieces shall provide access for persons desiring to enter the laser usage area.
If the curtain is parted wide enough, however, (e.g. for equipment access) an interlock sewn into the curtain shall activate and the laser(s) will be de-energized.
Please contact the NC State Laser Safety Officer for preferred equipment. Refer to the next section for a description of the interlock and shut-down circuit.
An electrical control circuit shall be installed in the laboratory for the primary purpose of shutting down laser operation in the event that one or more of the following occurs:
Refer to the schematic. The control circuit is typically housed in an electrical panel labeled “Laser Control Panel”. A 24VAC control transformer feeds an interlock loop comprising of various elements required for the laboratory: curtain and door interlocks, laser kill switch, and other interlocks deemed necessary for laser safety can be added to this loop.
drawing shows a typical class IV laser laboratory. Entry into
the lab is gained via coded cipher lock. The number is given to authorized
personnel only. An illuminated sign visible outside the main lab entry would
be lit if a laser were in use inside the lab. "In use" means that
the laser has power to its power supply and is capable of producing a beam.
A self-closing apparatus will close the door behind the user entering the
safety goggles are selected at this point from the eyewear station
located inside the protected entryway .
An emergency laser beam off switch is located just inside the door, as shown, and is available to emergency responders to cease laser beam operation before entry. A second laser stop switch may be located in the laser usage area and be available to lab occupants.
The curtain is parted and the user may enter the laser usage area via
the curtain overlap without breaking the pull-apart interlock. A secondary
exit may be equipped with a "hard interlock" as shown. This
switch action will cease laser operation when the door is opened and can
not be defeated. Within the lab are located the start / stop controls
for the laser power supply which are wired similar to the supplied schematic.
Refer to the circuit description in the previous section. Window panels
in doors should be covered or replaced with an opaque material. In general,
windows in the laboratory are covered both for light level control and
to contain stray beams so that they are not reflected outside. All class
IV laser labs should be equipped with smoke detectors, sprinkler heads,
and fire alarm annunciators. Gases required for excimer lasers require
gas cabinets with adequate exhaust and an exhaust monitoring device, additional
sprinkler heads, and a gas detection system wired for fail-safe shutdown.