Revision 1/2020


This Fact Sheet applies to equipment and appliances used in a laboratory. It does not address computers or other office equipment used in non-laboratory settings.  This Fact Sheet provides some basic guidance for commonly encountered electrical concerns in laboratories.

Extension Cords

Use extension cords for temporary (less than three months) use. Situations that require extension cords for greater than three months are considered permanent installations and must be addressed through upgrades to building wiring systems. Extension cords must be appropriately rated for the intended load.

Do not place extension cords in foot traffic areas or under equipment. Length shall be the minimum required for the specific application but shall not exceed 15 feet. Ground wires are required for all extension cords (i.e., the cord should have three prongs).  Extension cords must be plugged directly into a receptacle and cannot be daisy chained.

Power Strips

Power strips/surge protectors must be listed or labeled by a nationally-recognized testing laboratory such as Underwriter’s Laboratories Inc. (UL) and have a built-in circuit breaker to protect against overloading.  They must be plugged directly into a receptacle (not daisy chained or plugged into extension cords) and must be rated for the current and voltage connected to them.  

Single Conductor Wires

Single conductors shall not conduct greater than 24 volts. Code single conductors red or black and keep them as short as possible. Single conductors shall be a single continuous length of wire unless spliced or joined in a grounded electrical box that provides appropriate strain-relief. Wire nut or other connections that are not housed in a grounded electrical box are not permitted.

Terminal Connections

All electrical connections at the supply end (bus bars) for 24 volt or greater services shall have strain relief and be enclosed. Label the enclosure with the voltage.

Plug style connections are permitted if the conductor is fully insulated and the conducting wire is not exposed when disconnected.

When possible enclose electrical connections in a protective housing. Insulate high temperature (>1808C) connections, such as furnaces, with 3M 69 Class "H" glass cloth tape (call Chemistry department or LRSM stockrooms for availability).

Exposed energized connections are not permitted.

Electrical Equipment Modified by or Built by Lab Workers

Download the policy in the Electrical Safety section of the EHRS website under "Related Content" > "Lab and Support Shops"

This excerpt (Section 11) from Penn’s Electrical Safety Program defines practices and procedures to be implemented for electrical equipment that is not listed or labeled by a nationally-recognized testing laboratory (NRTL). Typically, this will include research related equipment that is custom built in-house or NRTL-listed or labeled equipment that has been modified which invalidates the listing or labeling.

Other resources:

Occupational Safety Fact Sheet on Electrical Safety

Electrical Safety