Class IV Laser Controls -
General Requirements
Those items recommended for Class IIIB but required for Class IV lasers are
as follows:
- Supervised directly by an individual knowledgeable in laser safety.
- Require approved entry of any non-involved personnel.
- Terminate all potentially hazardous beams in a beam stop of an appropriate
material.
- Use diffusely reflecting materials near the beam, where appropriate.
- Personnel within the laser controlled area are provided with appropriate
laser protective eyewear.
- Secure and locate the laser such that the beam path is above or below eye
level in any standing or seated position.
- Have all windows, doorways, open portals...etc. from an indoor facility covered
or restricted so-as-to reduce transmitted beams below appropriate ocular MPE level.
- Require storage or disabling of lasers when not in use.
Entryway Control Measures (Class IV)
In addition, there are specific controls required at the entryway to a Class
IV laser controlled area. These can be summarized as follows:
- All personnel entering a Class IV area shall be adequately trained and provided
proper laser protective eyewear.
- All personnel shall follow all applicable administrative and procedural controls.
- All Class IV area/entryway controls shall allow both rapid entrance and exit
under all conditions.
- The controlled area shall have a clearly marked "Panic Button" (disconnect
switch) that allows rapid deactivation of the laser.
In addition, Class IV areas also require some form of area-entryway controls.
In the past, doorway interlocking was customary for Class IV installations. Now,
the ANSI Z-136.1 (1986) standard provides three options that allow the LSO to
provide an entryway control suited for the installation. The options include:
- Non-defeatable Entryway Controls:
A non-defeatable control, such as a magnetic switch built into the entryway door
which actuates a "beam off" condition when the door is opened is one option. In
this case, training is required only for persons regularly working in the laser
area.
- Defeatable Entryway Controls:
Defeatable controls may be used at an entryway, for example, during long term
testing in a laser area. In this case the controls may be temporarily by- passed
if it is clearly evident that there is no hazard at the point of entry. Training
is required for all personnel who frequently require area entry.
- Procedural Entryway Controls:
A blocking barrier, or screen, or curtain which can block or filter the laser
beam at the entryway may be used inside the controlled area to prevent the laser
light from exiting the area at levels above the applicable MPE level. In this
case, a warning light or sound is required outside the entryway that operates
when the laser is energized and operating. All personnel who work in the facility
shall be appropriately trained.
