June 8, 1992

Melvin L. Henry
Electrical Supervisor
Gasbarre Products, Inc.
590 Division Street
Dubois, PA 15801

Dear Mr. Henry:

This letter is in response to your questions concerning whether capacitive sensor palm buttons would:

* be considered to be a presence sensing initiating device which is regulated by 29 CFR 1910.217(h)

* be acceptable in lieu of conventional mechanical spring loaded palm buttons for mechanical press guarding operations.

In response to your first question, a capacitive sensor palm button is not considered to be a presence sensing initiating device as that term is used in OSHA Standard 29 CFR 1910.217(h). Capacitive sensor palm buttons are activated by the presence of an object in the sensing field that is created near the surface of the presence sensing palm button. A "presence sensing device" however, differs from a presence sensing palm button in that they "create a sensing field or area that signals the clutch/brake control to deactivate the clutch and activate the brake of the press when any part of operator's body or a hand tool is within such a field".

It should be noted that there is at least one other type of palm presence sensing device that utilizes a sensing method different than that used by the capacitive palm sensor buttons. These types utilize a "break beam" system whereas a beam is generated and when an object breaks the beam the palm sensing device functions.

In response to your second question, capacitive sensor palm buttons may be acceptable in lieu of conventional mechanical spring loaded palm buttons as two hand trips or two hand controls. We have requested that our National Office evaluate the acceptability of both the capacitive and the break beam devices. This request was made because when the acceptability of these devices was being evaluated a question arose as to whether some of these presence sensing palm buttons were designed so as to prevent unintended operation. The specific question at issue is whether any of these devices could be inadvertently activated by objects other than a hand, i.e. could clothing passing through the sensing field cause the devices to operate. The National Office will respond to you directly on this matter.

If you have any questions regarding this matter you may contact the Office of General Industry Compliance Assistance at (202) 523-8031.

Sincerely,



LINDA R. ANKU
REGIONAL ADMINISTRATOR