Chris, I am by no means an expert here as I have only been doing compliance about 2 years. Most of my experience is in I.T.E. i.e. UL 1950, IEC 950, etc. We have just recently started doing products that are tested under UL 3111-1, EN6101-1, IEC 1010-1, etc. I am basically going by what the standards say and what has been my personal experience.
In my copy of IEC 1010-1 it only lists two different pollution degrees, 1 and 2. 3.7.2 POLLUTION: Any addition of foreign matter, solid, liquid or gaseous (ionized gases), that may produce a reduction of dielectric strength or surface resistivity. 3.7.3 POLLUTION DEGREE: For the purpose of evaluating CLEARANCES the following two degrees of POLLUTION in the micro-environment are recognized for use with this part 1. 3. 7.3.1 POLLUTION DEGREE 1: No POLLUTION or only dry, non-conductive POLLUTION occurs. The POLLUTION has no influence. 3.7.3.2 POLLUTION DEGREE 2: Normally only non-conductive POLLUTION occurs. Occasionally, however, a temporary conductivity caused by condensation must be expected. Now here is where the I.T.E. standards differ from the test equipment standards. In UL 1950, EN60950, etc. there are three degrees of pollution. First of all here is what the workbook that I received at a UL 1950 seminar held by UL in 1998 has to say: Pollution Degree 1: No pollution. Hermetically sealed Pollution Degree 2: Nonconductive Pollution. Might become temporarily conductive because of condensation. Pollution Degree 3: Conductive Pollution OR Nonconductive Pollution which could become conductive due to expected condensation. >From EN 60950: 2.9.1 The values for Pollution Degree 1 are applicable to components and assemblies which are sealed so as to exclude dust and moisture (see 2.9.6) The values for Pollution Degree 2 are generally applicable to equipment covered by the scope of this standard. The values for Pollution Degree 3 are applicable where a local internal environment within the equipment is subject to conductive pollution or to dry non-conductive pollution which could become conductive due to expected condensation. 2.9.6 Enclosed and Sealed Parts For components or subassemblies which are adequately enclosed by enveloping or hermetic sealing to prevent ingress of dirt and moisture, the values for Pollution Degree 1 apply to internal CLEARANCES and CREEPAGE DISTANCES. In looking at these standards it appears that the definitions for 1 and 2 align pretty closely. The Pollution Degree 3 in the 1950 standards does not appear to have an equivalent in the 1010 standards. (Maybe I.T.E. can be used in a more polluted environment than test equipment). We always do our PC boards based on Pollution Degree 2. For internal layers you can use Pollution Degree 1. Also in the UL 1950 workbook from the UL seminar it specifically states "Office Environment-Pollution Degree 2" It also states that it us necessary to consider the amount of pollution in a given environment when coordinating insulation. - macro environments -- micro environments. It shows as an example a copier. The entire copier is in a Pollution Degree 2 environment. There is a High Voltage Power Supply within the copier that is encapsulated in epoxy. The environment inside this Power Supply is Pollution Degree 1. It shows that in the area of the Toner Cartridge that it is Pollution Degree 3. So I would say that for most things for an indoor environment you should use Pollution Degree 2. Kurt Andrews Compliance Engineer Tracewell Systems, Inc. 567 Enterprise Dr. Westerville, OH 43081 Ph. 614-846-6175 Fax 614-846-7791 Email: [email protected] -----Original Message----- From: Chris Wells [SMTP:[email protected]] Sent: Sunday, January 16, 2000 8:00 AM To: 'emc-pstc' Subject: pollution degree 1? 2? Kurt In your feedback (thank you!) you state that pollution degree 1 is for conditions with NO pollution at all like a potted epoxy environment. This is the impression I got from UL and other sources. Help me out here please. From my memory the definition in EN61010-1 (same as in IEC 664) Pollution degree 1 is for non conductive dust environments - no condensation. Pollution degree 2 is for non conductive dust environments - occasional condensation Pollution degree 3 is for conductive dust environments. The definition for pollution degree 1 implies that this is a standard office like environment. Am I missing something here? Do most PCB spacings get evaluated to pollution degree 2? in ITE? in Automation equipment like Programmable Logic Controllers ? Thanks . Chris Wells Senior Design Eng Cutler-Hammer Pittsburgh Pa [email protected] Original Message----- From: Andrews, Kurt [mailto:[email protected]] Sent: Monday, January 10, 2000 12:14 PM To: Price, Ed; '[email protected]' Cc: 'Chris Wells' Subject: RE: Pollution degree help Ed, Chris, Normally Pollution Degree 1 is used for items that receive no pollution at all. These are hermetically sealed or potted/encapsulated parts. However you can use pollution degree 1 for internal PCB layers. <snip> --------- This message is coming from the emc-pstc discussion list. To cancel your subscription, send mail to [email protected] with the single line: "unsubscribe emc-pstc" (without the quotes). 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