The Occupational Health and Safety Administration provides the following guidelines for the use of tags in the lockout/tagout program:
1910.147(c)(7)(ii)(A) Tags are essentially warning devices affixed to energy isolating devices, and do not provide the physical restraint on those devices that is provided by a lock.
1910.147(c)(7)(ii)(B) When a tag is attached to an energy-isolating means, it is not to be removed without authorization of the authorized person responsible for it, and it is never to be bypassed, ignored, or otherwise defeated.
1910.147(c)(7)(ii)(C) Tags must be legible and understandable by all authorized employees, affected employees, and all other employees whose work operations are or may be in the area, in order to be effective.
1910.147(c)(7)(ii)(D) Tags and their means of attachment must be made of materials which will withstand the environmental conditions encountered in the workplace.
1910.147(c)(7)(ii)(E) Tags may evoke a false sense of security, and their meaning needs to be understood as part of the overall energy control program.
1910.147(c)(7)(ii)(F) Tags must be securely attached to energy isolating devices so that they cannot be inadvertently or accidentally detached during use.
OSHA defines various kinds of hazardous energy sources as deriving from "electrical, mechanical, hydraulic, pneumatic, chemical, thermal or other sources in machines and equipment."
In keeping with OSHA compliance and guidelines, tags need to reflect these energy sources in the relevance of warning messages they convey when a piece of equipment is compromised.
The National Institute of Occupational Safety and Health (NIOSH) in its recommendations to OSHA "Guidelines for controlling hazardous energy during maintenance and servicing," (September 1983) identifies four types of energy as kinetic (involving motion), potential (involving energy produced by gravity), electrical, and thermal, which may involve mechanical, radiation, chemical reaction or electrical resistance.
Given these definitions of energy, tag compliance should logically follow the nature of the energy being disabled. Tag types can be illustrated in terms of need for hazardous energy exposure risk as follows:
Mechanical (kinetic) energy will usually involve some type of equipment or machinery. Tags such as "Do not operate," "Hands off," "Unsafe do not ise," "This energy source has been locked out," "Do not start this machine," are among the kinds of tags most relevant in these cases.
A "Locked out" tag will sometimes carry a photograph of the operator with the legend, "My life is on the line," humanizing the threat to safety.
Energy source tags that indicate the kind of hazardous energy present — electric, hydraulic, pneumatic, thermal, mechanical — and also more specific types of energy such as steam, control gravity, gas and water.
Electrical energy would carry similar messages along with tags warning "Do not throw switch men working on circuit nearby," "High voltage," Disconnect before servicing," "Electrical hazard," "Caution" and "Danger" wall signs posted nearby warning that a locked out circuit breaker should only be operated by authorized personnel adds an extra layer of security. Entire panel boxes might carry multiple tags and locks.
Hydraulic energy sources may involve kinetic, potential or thermal energy and would carry warnings against operation at the source of energy release: a valve, pump, hose or hydraulic cylinder. These are referred to as machinery involving any energy source as "points of control." Securing points of control "prevents unauthorized personnel from reactivating the flow of energy." NIOSH tags should convey the message "Do not open valve" as well as include a hydraulic energy source tag.
Pneumatic energy involves air compressors, hoses, lines, and connectors and would be tagged at the source of energy hazard, a control switch, a shutoff valve, or a hose connection. A lockout placard of the procedures for lockout/tagout involved may also be displayed, depending on the level of complexity. Since many power tools involve pneumatic energy, there are multiple concerns at both the source of energy (the air compressor and its lines) and the tool itself, which may have cutting, hitting or rotary movement. A "Do not open valve" tag should be attached as well as a pneumatic energy source tag.
Chemical energy can occur in any number of settings where elements become reactive when combined, or when human contact is made with harmful substances. This includes bio-hazards, toxic substances, caustic liquids, and includes chemicals in gas form under pressure in cylinders such as argon and acetylene. "Right to know" informational tags are relevant in these instances where properties are indicated and protective gear recommended. "Do not open valve" tag as well as include a specific chemical tag.
Thermal energy also blurs the line between several other forms of energy when it comes to human exposure to the hazard. Thermal hazards include mechanical work, radiation, chemical reaction and electrical resistance. Warnings on tags should indicate flammable liquids and flammable materials. Thermal systems may also require a "Do not open valve" tag.