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Intrinsic Safety Approvals for Radio Communications Equipment

Overview and definitions

The following classification and rating details are only meant to be a guide for quick reference. We make no claims to the accuracy of the information below. Explanation of these classes, divisions and atmospheres can be found in Article 500 of the United States National Electrical Code.

What is Intrinsically Safe (IS)?
What is Non-Incendive (NI)?
What communication products carry safety certifications?

Typical Class I-III locations
Detailed list of groups
Temperature rating codes

Certifying Agencies for Hazardous Locations Equipment
Servicing of Intrinsically Safe Radios

What is Intrinsically Safe (IS) communications equipment?

Communications equipment that is incapable of releasing sufficient electrical or thermal energy under normal or abnormal operating conditions to cause ignition of a specific hazardous mixture and air. The IS rating is required for equipment to be used in Division 1 environments.


What is Non-Incendive (NI) communications equipment?

Communications equipment that is incapable of releasing sufficient electrical or thermal energy under normal operating conditions only which cause ignition of a specific hazardous mixture and air. The NI rating is required for equipment to be used in Division 2 environments.


What communication products carry safety certifications?

The following types of products may also be certified as Intrinsically Safe/Factory Mutual or Non-Incendive, when used together with approved radios:

Battery packs for portable radios
Battery chargers
Audio Accessories - earphones, headsets
Speaker Microphones
Signaling accessories and option boards - selcall, scramblers, DTMF, CTCSS, VOX



Intrinsically safe and Non-Incendive approvals are classified by classes, divisions, groups and a temperature rating. These are further defined as follows:

Class: this can be defined as relating to the industry type in which the equipment will operate.

Classes range from Class I to Class III, where

Class I is for such industries as petroleum/gas/oil
Class II - heavy engineering (such as iron -ore, magnesium, coal ,charcoal) and the food industry (starch, grain processing).
Class III is for industries dealing with fibers


Typical Class I-III locations are:

Class I (gas or vapors):

- Petroleum refineries, and gasoline storage and dispensing areas
- Dry cleaning plants where vapors from cleaning fluids can be present
- Spray finishing areas
- Aircraft hangars and fuel servicing areas
- Utility gas plants, and operations involving storage and handling of liquefied petroleum gas or natural gas.

Class II

- Grain elevators
- Flour and feed mills
- Plants that manufacture, use or store magnesium or aluminum powders
- Producers of plastics, medicines and fireworks
- Producers of starch or candies
- Spice-grinding plants, sugar plants and cocoa plants
- Coal preparation plants and other carbon handling or processing areas.

Class III

- Textile mills, cotton gins
- Cotton seed mills, flax processing plants; and
- Plants that shape, pulverize or cut wood and create sawdust or flyings
Class European IEC, Cenelec, NEC 505 codes N.A. NEC 500, CSA codes, UL® 913-88 Standards
Flammable Material Present
Continuously Present Zone 0 Division 1
Intermittently Present Zone 1 Division 1
Abnormally Present Zone 2 Division 2
Gas & Vapors Present
Acetylene Group IIC Class I/Group A
Hydrogen Group IIB Class I/Group B
Ethylene Group IIB Class I/Group C
Propane Group IIA Class I/Group D
Methane Group I N/A
Dust Present
Metal N/A Class II/Group E
Coal N/A Class II/Group F
Grain N/A Class II/Group G
Fibers (All) N/A Class III


Division: this can be defined as relating directly to the proximity of the risk. That is, is the hazardous mixture in direct contact with the environment (Division 1, closer proximity) or is it enclosed within a container or system or ventilated (Division 2, further proximity).


Group: this is the type of atmosphere and ranges from Group A through to Group G.

Group A covers atmospheres containing Acetylene gas.
Group B covers atmospheres containing Hydrogen gas. Both A and B are very unstable and explode at low temperatures.
Group C covers vapors of Ethylene.
Group D covers Propane vapor atmospheres.
Group E includes atmospheres containing various types of metal dust.
Group F has coal dust.
Group G contains grain dusts.


For detailed list of groups see below:


Group A Atmospheres

Atmospheres containing Acetylene gas.

Group B Atmospheres

Atmospheres containing Hydrogen gas.

Group C Atmospheres Chemical (Ethylene based)
2-nitropropane Acetaldehyde allyl alcohol
carbon monoxide crotonaldehyde cyclopropane
diethyl ether Diethylamaine epichlorohydrin
ethyl mercaptan ethyl sulphide ethylenimine
hydrogen cyanide hydrogen sulphide Morpholine
n-butyraldehyde tetrahydrofuran UDMH 1, 1-dimenthyl hydrazine
unsymetrical dimethyl ethylene    
Group D Atmospheres Chemical (Propane based)
1-butanol (butyl alcohol) 1-pentanol (amyl alcohol) 1-propanol
2-butanol (secondary butyl alcohol) 2-methyl-2-proponal 2-methyl-l-proponal
2-propanol 3-methyl-l-butanol acetic acid
Acetone acrylonitrile ammonia**
Benzene Butane di-isobutylene
Ethane ethanol (ethyl alcohol) ethyl acetate
ethyl acrylate (inhibited) ethylene diamine ethylene dichloride
ethylene glycol monomethyl ether Gasoline Heptanes
Hexanes isobutyl acetate Isoprene
isopropyl ether mesityl oxide methane (natural gas)
methanol (methyl gas) methyl ethyl ketone methyl isobutyl ketone
n-butyl acetate octanes pentanes
petroleum naptha* propane propylene
pyridine styrene toluene
vinyl acetate vinyl chloride xylenes

* Saturated hydrocarbon mixture boiling in the range of 20-135 ° C (68-275 ° F). Also known by the synonyms benzene, ligroin, petroleum ether or naphtha.

** For classification of areas involving ammonia atmosphere, see Safety Code for Mechanical Refrigeration (ANSI/ASHRAE 15-1978) and Safety Requirements for the Storage and Handling of Anhydrous Ammonia (ANSI/CGA G2.1-1972)

Group E Atmospheres

Atmospheres containing metal dust, including aluminum, magnesium and their commercial alloys, and other metals of similarly hazardous characteristics.

Group F Atmospheres

Atmospheres containing carbon black, charcoal or coke dusts which have more than 8 percent total volatile material (carbon black per ASTM D1620, charcoal, coal and coke dust per ASTM D271) or atmospheres containing these dusts sensitized by other materials so that they represent an explosion hazard.

Group G Atmospheres

Atmospheres containing flour, starch, grain or combustible plastics or chemical dusts.



Temperature rating is probably the most important factor for IS portable radios. The temperature rating is a maximum temperature ( ° C) with an associated identification code.
The temperature rating means that where any hazardous mixture explodes or combusts at less than the stated maximum temperature, then the portable radio cannot be used in this environment. If units do not meet the temperature requirement then there is no basis for utilizing radios regardless of whether or not the units meet the other standards i.e. class, division and group.


Temperature Rating Codes

Identification Code Maximum Temperature (° C)
 T1  450
 T2  300
 T2A  280
 T2B  260
 T2C  230
 T2D  215
 T3  200
 T3A  180
 T3B  165
 T3C  160
 T4  135
 T4A  120
 T5  100
 T6  85


Certifying Agencies for Hazardous Locations Equipment

FM: Factory Mutual Research Corporation

The Factory Mutual Approvals Division determines the safety and reliability of equipment, materials, or services utilized in hazardous locations in the United States and elsewhere. Factory Mutual certifies to NEC (National Electrical Code) standards for hazardous locations, NEC Standard 500 (Division classification) and also to the new NEC Standard 505 (Zone classification), which attempts to harmonize American and European classifications. For a product to receive approval, it must meet two criteria:

First, it must perform satisfactorily, reliably, and repeatedly as applicable for a reasonable life expectancy.

Second, it must be produced under high quality control conditions. Factory Mutual also has interlaboratory agreements and can certify to Canadian and European standards.

CSA: Canadian Standards Association

The association includes Canadian consumers, manufacturers, labor, government, and other regulatory agencies among its actively participating influences. These groups work together to generate standard requirements (CSA standards) that demonstrate product quality, enhance market acceptability, and improve quality and safety control procedures in manufacturing and construction for the Canadian marketplace. The standards generated by CSA are the cornerstone for determining a product's eligibility for certification in hazardous locations in Canada. CSA also performs product evaluation, testing, and ongoing inspection to these standards, and also to American and European standards through new interlaboratory agreements.


These are some of the recognized European approval agencies that have certified portable radios to Cenelec (European Committee for Electrotechnical Standardization) and/or IEC (International Electrotechnical Commission) standards for hazardous locations. Cenelec attempts to harmonize the electrical standards of its member countries. Generally, IEC standards are used. However, in certain instances where IEC standards are considered too vague, Cenelec defines more precise requirements. The member nations of Cenelec, which include and exceed those of the EEC (European Economic Community), are bound to adhere to these international regulations.

CE Marking

"CE" marking is a declaration from the manufacturer that their product conforms to a specific Directive(s) adopted by the EEA (European Economic Area) and is a requirement for the product to be sold into any of the countries in this 18 member group. CE is an abbreviation for the French phrase Conformité Européene, meaning European Conformance. Unlike hazardous location approvals, the manufacturers are solely responsible for ensuring their product's conformance to these Directives which were developed using IEC and Cenelec standards. The Directives that affect only radio communications equipment are known as the EMC (Electromagnetic Compatibility) 89/336/EEC and LVD (Low Voltage) 73/23/EEC Directives.

These state that the products must meet specific electromagnetic emission and immunity, as well as electrostatic discharge standards. Transmitters that meet EMC standards, as declared by the manufacturer, must be able to withstand interference from the radio frequency spectrum, electrostatic discharge, surges, etc., without the unit's performance being affected. The transmitter must also emit a minimum of the above charges so that it does not affect other nearby electrical devices or systems such as emergency communications or radio and television broadcasts. The Low Voltage Directive addresses basic electrical shock and fire hazard issues. These directives are currently only a requirement for the EEA member nations and are not required for products sold outside this community.


ATEX Directive (94/9/EC) is the latest European regulation related to equipment and protective systems intended for use in potentially explosive atmospheres. It came into force on 1st July 2003.

It covers all mechanical and electrical equipment and protection systems used under ground, on the surface, fixed Installations offshore excluding maritime usage.

Countries covered by the directive are all the European Union (EU) countries plus the European Free Trade Area (EFTA) countries: Belgium, Denmark, Germany, Greece, Spain, France, Ireland, Italy, Luxembourg, Netherlands, Austria, Portugal, Finland, Sweden, U.K. and European Free Trade Area (EFTA) countries: Liechtenstein, Iceland, Norway, Switzerland.

For more information, please refer:
Motorola ATEX Directive.pdfAdobe Acrobat Document, PDF(75.13 KB)
Motorola ATEX equipment.pdfAdobe Acrobat Document, PDF(20.07 KB)


Servicing of Intrinsically Safe Radios

Any IS-rated communication product must be serviced at at the appropriate manufacturing facilities, in order to maintain its rating. Under no circumstances should it be serviced at the branch level or an outside shop. A requirement of the IS approval process from the Factory Mutual Corporation (approval body) demands that the radios are serviced at an audited plant.


NB: We cannot advise our customers what ratings of radio equipment they would need for their work environment, for reasons of liability.
There are a number of publications which detail combustion thresholds of hazardous mixtures and the customer should research this themselves.

Information: Courtesy of OSHA, Flow-Tech Inc., Tait Electronics Ltd

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