Battery Powered Tools in Hazardous Location (02-01-02)

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Mike, I am a chemical engineer at Arch Chemicals. People have asked me several times if it is code compliant to use battery powered equipment in Class 1 Division 1 or Class 1 Division 2 areas. I have looked in the NEC and have not found anything on low voltage battery powered equipment. I have always defaulted to using equipment in nitrogen-purged boxes if they are not intrinsically safe or do not meet the code requirements. Could I use a small scale that is powered by a battery pack that could be charged as high as 14.5 volts?

Please let me know as this question has been gnawing at me for three years. I would love to be able to give my safety department a definite answer.

From Vickers, Julie C. MESA

Process Engineer, Arch Chemicals

From: Kain, Steve

The NEC does not differentiate between voltage levels or battery/line powered devices in Class I, Division 1 or 2 locations. The mandate is to ensure that energy accidentally released because of a circuit fault is below the minimum energy required to ignite whatever gas or material is present in the atmosphere. If this is not possible, the conductors/electronics/contacts/equipment must be enclosed in an explosionproof enclosure, which cools the exhaust gasses below the temperature required to ignite the atmosphere. NEC requirements are:

1) Apparatus must be classified as explosionproof or

2) Enclosure must be purged and pressurized in accordance with NFPA 496-1998 or

3) All circuitry must be classified as "Intrinsically Safe" or

4) Device may be enclosed in an oil bath or

5) Device may be hermetically sealed such that no external atmosphere can penetrate to electronics/contacts/wiring.

From: arcs and sparks

I never thought about blowing myself up to the carpenter in the sky by using a cordless tool... I suppose its possible huh...maybe she should use air tools with lots of hose:)

From: Dale Kessler

First, I would need to know the type of facility in which this equipment is being placed. This would, in my opinion determine the NFPA Standard, which would cover the operation. Is this chemical plant, refinery, or distillery? It makes a big difference. I do not believe that voltage is the issue. The ability to generate a source of ignition is the key. Non-incendive circuits and equipment rated for the environment. If the manufacturer does not make a housing suited for this environment then he is back to a nitrogen purge.

However, in my experience there is usually another way. Longer leads to a safe area, explosion proof housings, properly rated equipment. Remember if do not produce enough heat to exceed the auto-ignition temperature you cannot have a fire. Again, it comes down the governing body having jurisdiction. They would also be a great source of information. No one wants an unsafe installation.

From: Rowland, John

The answer to the question is to refer to NEC 500-4 where it refers to the ANSI/ISA S12.12-1994 standard on Nonincendive Electrical Equipment for use in Class I and II, Division 2 and Class III, Divisions 1 and 2 Hazardous (Classified) Locations. If you go to the charts, you will find the igniting currents say for example for hydrogen - 12 volts and 5 amps. Using this information and the flashpoint or auto-ignition point to as a test against any hot components then an engineering judgment call can be made to you concern. One thing to keep in mind is the battery. The non-incendive batteries have a SCR type current limited circuit to shut off the battery if a short or high current occurs beyond the battery terminals. If you device has a current limiting fuse that could serve as the same purpose. Motorola uses the SCR and just by changing batteries, their radio can be for use in a Division 1 area.

From: John Doty

We are also working on getting hazardous location UL1604 approval for a battery based system - only ours is using a large 100Ahr+ battery for solar electric applications. There are many issues to resolve and any information on the topic would be greatly appreciated.

From: Roger Strand

I am of the opinion that unless the item is specifically listed for Class 1 Division 1 or Division 2 it does not belong in that atmosphere. There is enough stored energy to cause ignition in most all of these devices. I know that flashlights used in these atmospheres have to be explosion proof. I do not see any reason that makes other battery devices have any less stringent requirements.

From: Tom Baker

Look at the UL Red Book "Hazardous Locations Equipment Directory”. Equipment that is UL Listed for the hazardous location is listed, from baby bassinets to flashlights. The UL Red Book (and any of the UL books) is valuable in that there is general application information on each listing category. You should consult the following standards:

UL Standard UL913 "Intrinsically Safe Apparatus and Associated Apparatus for use in Class I, II and III, Division 1, Hazardous Locations"

UL Standard UL1604 "Intrinsically Safe Apparatus and Associated Apparatus for use in Class I, II and III, Division 2, and Class III Hazardous Locations"

Note. There are products listed by other testing labs, which would not be shown in the UL directories. In addition, some testing labs will use the UL standards with their product evaluations and listing.

I do not believe I have ever seen a listed C1 D1 or D2 battery tool, such as a drill for a hazardous classified area. The reasons may be a limited market or the expense of listing and labeling.

From: Denise Sullivan

Interesting question, been discussed for years without an officially documented answer. The closest I can respond is a meeting I had with an OSHA Field Representative for the Northeast. His decision indicates that not all cordless tools are the same, and I had to verify that the tool would NOT produce a spark around the armature when in use. He did this by testing it in a confined space with an Argon gas. He also required that the battery for the tool be removed and inserted outside the confined area of work. The company I was working in uses battery-powered scales in all three of their main production areas. The OSHA inspector indicated the battery change sequence was the only requirement he wanted implemented.

This occurred in year 1997, about August, in a paint manufacturing plant in Mass. The plant is part of an International Company, so I would have to gain their permission to forward any written documents.


Contact the manufacturer and ask them to supply you with the specifications as to whether it is "Explosionproof" equipment. I would also contact Underwriters Labs to see if is listed for Hazardous environments. Otherwise, just one little spark will ruin your whole day.

From: Lynn Adams

While the low voltage equipment may seem safe and non-threatening, I would not recommend its use. The equipment is neither sealed to prevent the entry of explosive gasses/contain and cool the products of combustion, nor is it of sufficiently low power to be intrinsically safe. Likely, it could be used for many times without incident - BUT we must protect against explosive hazard under abnormal and fault conditions as well.

The average batter pack is sufficient to cause a spark. To evidence this, take a wire and cross the two ends of a simple 1.5 volt D battery. Momentary contact will cause a substantial spark; continuous contact can heat the wire to ignition temperature. Note that there are flashlights approved for use in mines and hazardous locations. They include provisions to disconnect the battery from the lamp if the outer envelop of the bulb is shattered.

From: Don Edgerley

Please be extremely cautious with any power tool ac or battery powered in a hazardous location they have armatures that spark. My thoughts would be to use pneumatic tools in a hazardous location and non-spark tools that were made of brass or aluminum or a material that would not produce a spark. I at times work in areas with gases that would explode and even if the area was purged, there is always the chance of a little gas there. Check with a local Fire Department, they may be able to point you in the right direction.

From Rich Burman, UL

Hi Mike, Hopefully, this information will help resolve the controversy. First, it should be noted that technically the NEC does not apply to portable, battery-powered devices. The Article 100 definition of "equipment" states that the "equipment " is part of an electrical installation. These devices, since they do not connect to the electrical power that is part of the installation, are not covered by the NEC. That is not true of portable, cord-connected equipment (see 501-11 for example). The fact that the NEC does not cover does not apply to portable, battery-powered devices does not mean that they are not a potential source of ignition. NEC Panel 14 accepted a proposal to focus on this subject, due to the widespread use of cell phones, pagers, etc. in classified areas. If ultimately accepted, it would include these devices within the scope of Chapter 5 of the NEC.

Although the NEC does not currently cover these devices, they still pose a potential risk of ignition, and need to be suitable for the area they will be used. In Class I, Division 1 locations, the permitted protection techniques are:

  1. Explosionproof
  2. Intrinsically Safe
  3. Purged/Pressurized

In Class I, Division 2 locations, they are:

  1. Any of the above for Division 1
  2. Nonincendive circuits, components, equipment
  3. Hermetically sealed or sealed components
  4. Oil immersion

UL Lists battery operated devices for both Division 1 and 2, but these are mostly gas detectors, pagers, and instruments of various types, but no power tools. For tools, it is very difficult to comply with any of the above protection techniques for various reasons. In most well regulated facilities, they either use air-operated tools or get "hot work" permits before using the tools in classified location.

Rich Berman, Research Manager

Underwriters Laboratories Inc.