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NRTL listing for Intrinsically Safe - Hazardous Area Classification

NRTL listing for Intrinsically Safe - Hazardous Area Classification

NRTL listing for Intrinsically Safe - Hazardous Area Classification

We want to buy a European intrinsically safe ultrasonic meter for our USA manufacturing site.  The classification of our site is Class I, Div 1, Group C, and also Class II, Div 1, Group G.  The device has the following listing:

Ex ia IIc T3/T2 Ga

Examining the listing into its components I read:
EX ia – means intrinsically safe for Class I, Zone 0 areas (equivalent to our Div 1)
IIC- Atmospheres of acetylene, hydrogen (NEC FPN Group IIC is equivalent to Classs I, Group A)

T3/T2  Temperature code  same as NEC 300/200C   (don't know why there are two temps)

Ga – describes the type of protection 'very high' in this case.

However, NEC 504.4 "All intrinsically safe apparatus and associated apparatus shall be listed.  Exception: Simple apparatus"
This device does NOT meet 'simple apparatus as defined in 504.2 (at least to that I can see based upon its opera ting voltage of 20.4 volts

Listed, usually means by a NRTL (nationally recognized testing laboratory) and it would typically include the Class, Division, and Group on the nameplate.  

It was my understanding that the European listing was one self certified by the company.

Do you believe that this IEC listing is sufficient for the USA classes mentioned?

Do you thing NEC wants to see a label other than saying 'Intrisically Safe' but also wants Class, Div, and Group on the label.

Appreciate any advise.

RE: NRTL listing for Intrinsically Safe - Hazardous Area Classification

NRTL = Nationally Recognized testing Laboratory. National in this case is referring to the Nation you are working in.

Your local inspector and/or insurance underwriter, when deciding on compliance to the NEC, will be looking for NRTL listing from one of the specific RECOGNIZED testing labs in the list maintained by OSHA.


If you will notice, "IEC" is not on that list. IEC is not an independent testing authority or lab, it is a collection of standards by which subscribing countries, and the manufacturers of products to serve those markets, agree to adhere. But it is left to the companies to claim adherence or not, kind of like the "honor system" but with some fairly dire consequences. But here in the litigious US (and Canada) we don't allow self certification, we insist on 3rd party testing and approval, the cost burden of which is typically borne by the manufacturer. If you are wanting to use a product that the manufacturer in Europe seems to think is not worthy of paying for NRTL listing for, I would be concerned for the long term viability and support of it in North America. Something to consider in your decision process.

My frequent advice on issues like this is to evaluate your risk and cost of down time against the benefits of whatever features that you think you can't live without which are missing from locally listed product. If your supplier is unwilling to bear the cost of doing business in N. America, the chances of them getting a replacement unit to you in short order may slim.


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RE: NRTL listing for Intrinsically Safe - Hazardous Area Classification

Have you talked to the device manufacturer about if they are self certified or if they can produce test documentation from a NRTL?  

I design to the IEC standards all the time, because I want to sell here in the USA and also in other countries.  My NRTL knows how to translate if necessary, but with the standards being harmonized this is rarely required.  


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