RE: Hot Surface. Hot air.
Of course a piece of metal is really hot at 70 degrees ! One should keep in mind that safety standards are related to safety, not to prevent discomfort. Even when falling onto it, one may rise (and shine) before a serious burn occurs. 70 degrees C (25+45) is a well established limit throughout many many safety standards and can be used as a general no further test required signal for office and IT equipment. ( seen from the point of customer; not the test house ;)) The heated air issue is very different, remember a sauna where the Finnish (and many others), use to stay for over 30 minutes at over 80 degrees before jumping into the snow, and compare that to the serious injuries one gets when touching the air/vapor mixture coming for a cookery pan. Humidity is an issue here. Air flow speed is too ! Regards, Gert Gremmen Ing. == Ce-test, Qualified testing == Consultants in EMC, Electrical safety and Telecommunication Compliance tests for European standards and ce-marking Member of NEC/IEC voting committee for EMC. Our Web presence: http://www.cetest.nl List of current harmonized standards http://www.cetest.nl/emc-harm.htm 15 great tips for the EMC-designer http://www.cetest.nl/features01.htm -Original Message- From: owner-emc-p...@majordomo.ieee.org [mailto:owner-emc-p...@majordomo.ieee.org] On Behalf Of Israel Yeshurun Sent: donderdag 7 oktober 1999 12:43 To: 'emc-p...@ieee.org' Subject:Hot Surface. Hot air. Dear Group Fellows I would like to raise the following two issues: 1) UL1950 / EN60950 Safety standards, Subclause 5.1 - Heating, Table 16 part 2, specify permissible temperature rise for external surfaces of equipment in Operator Access Area.. For external surfaces, made of metal which may be touched, it allows temperature rise of 45 degrees Kelvin, assuming ambient temperature of 25 degrees Celsius it allows surface temperature of 70 degrees Celsius = 158 degrees Fahrenheit ! Note (4) in this table applies to external surfaces that are not likely to be touched in normal use and measure less than 50 mm, in this case it allows a temperature rise of 75 degrees K, that under 25 degrees C ambient allows 100 degrees C = 212 degrees F !! Now, 70 degrees C for external equipment surface that may be touched seems pretty high to me. 100 degrees C metal surface will, I believe, cause a burn to that part of the human body that touched it. So maybe my interpretation is not true ??and, can someone point another regulatory source for Hot surface permissible temperature ? 2) Regarding Hot air flowing out of equipment, in UL1950 / EN60950 I could not find a requirement or limit for the maximum permissible temperature for it, Can someone point another regulatory source for Hot air permissible temperature ? Note: The equipment I relate to is ITE or Office, but information from Machinery standards or other sources is welcome ! Many Thanks Israel Yeshurun - This message is coming from the emc-pstc discussion list. To cancel your subscription, send mail to majord...@ieee.org with the single line: unsubscribe emc-pstc (without the quotes). For help, send mail to ed.pr...@cubic.com, jim_bac...@monarch.com, ri...@sdd.hp.com, or roger.volgst...@compaq.com (the list administrators). - This message is coming from the emc-pstc discussion list. To cancel your subscription, send mail to majord...@ieee.org with the single line: unsubscribe emc-pstc (without the quotes). For help, send mail to ed.pr...@cubic.com, jim_bac...@monarch.com, ri...@sdd.hp.com, or roger.volgst...@compaq.com (the list administrators).
Re: Hot Surface. Hot air.
Now, 70 degrees C for external equipment surface that may be touched seems pretty high to me. 100 degrees C metal surface will, I believe, cause a burn to that part of the human body that touched it. So maybe my interpretation is not true ??and, can someone point another regulatory source for Hot surface permissible temperature ? Israel, As others have pointed out - EN 563 can be used as a regulatory source. The standard ... applies to hot surfaces of all products and equipment that must or can be touched during their normal use. That includes the area of safety of machinery as well as any other applications. The standard does not apply, if a large area of the skin (approximately 10% or more of the skin of the whole body) can be in contact with the hot surface. This standard also does not apply to skin contact with more than 10% of the head or contact which could result in burns of vital areas of the face (e.g. burn resulting in the restriction of airways). In these cases severe injuries may occur, even if the surface temperature does not exceed the values specified in this standard. Does the EN 60950 consider these exceptions relevant? For your average office printer, PC, or monitor they probably aren't. There are however some fairly large equipment which are certified to this standard (mainframes?). You stated that 70 degrees C for external equipment surface that may be touched seems pretty high to me. Figure 2 of EN 563 indicates that at 70 degrees C, contact with a smooth uncoated metal surface for more than 1 second will result in a burn. For less than 1 second of contact time, there is no reliable data available (possible burn). Consider any forseeable problems - like someone falling onto your equipment. At 70 degrees, breaking a fall by placing your hands against the equipment could be rather unpleasant. And don't forget head contact. Regards, Matt - This message is coming from the emc-pstc discussion list. To cancel your subscription, send mail to majord...@ieee.org with the single line: unsubscribe emc-pstc (without the quotes). For help, send mail to ed.pr...@cubic.com, jim_bac...@monarch.com, ri...@sdd.hp.com, or roger.volgst...@compaq.com (the list administrators).
Re: Hot Surface. Hot air.
Hello Israel: Unfortunately, safety standards only address one of the critical parameters, temperature, when specifying requirements for protection against a burn injury. You are absolutely correct that a metal surface with a temperature exceeding 50 C is capable of producing a burn injury. There are four parameters that must be taken into account: 1. temperature 2. thermal conductivity of the material 3. thermal capacity of the material 4 duration of contact One can easily touch aluminum foil at 100 C and higher for an indefinite duration because its thermal capacity is very low. One can easily touch plastic at 100 C for an indefinite duration because its thermal conductivity is very low. One cannot touch a 25 mm or larger cube of aluminum at 50 C for longer than 10 seconds without burning the skin because its thermal conductivity and thermal capacity are high. There is no regulatory source that addresses all four parameters. Instead, you must consider your training in the field of thermodynamics, and you must consider the literature where the burn parameters of human skin are published. If you look, you will find published data relating skin temperature and duration to pain and to skin burns.** Unfortunately, the authors of our various safety standards chose the BOGSAT* method of determining safety rather than doing research. The requirements you mentioned are indeed inadequate. But, you have already determined that. So, using your training as an engineer, you can make your product safe for both the hot surfaces and the hot air in spite of the standard. Best regards, Rich - Richard Nute Product Safety Engineer Hewlett-Packard Company Product Regulations Group AiO Division Tel : +1 858 655 3329 16399 West Bernardo Drive FAX : +1 858 655 4979 San Diego, California 92127 e-mail: ri...@sdd.hp.com - * BOGSAT = Bunch Of Guys Sitting Around Talking. ** Stoll, Alice M., Thermal Properties of Human Skin related to Nondestructive Measurement of Epidermal Thickness, Journal of Investigative Dermatology, September, 1977, pp. 328-332. - This message is coming from the emc-pstc discussion list. To cancel your subscription, send mail to majord...@ieee.org with the single line: unsubscribe emc-pstc (without the quotes). For help, send mail to ed.pr...@cubic.com, jim_bac...@monarch.com, ri...@sdd.hp.com, or roger.volgst...@compaq.com (the list administrators).
RE: Hot Surface. Hot air.
Israel, There are only three temperatures to worry about: Hot, Damn Hot and Ouch. For something approaching a definition look in BS 4086 Recommendations for Maximum Surface Temperatures of Heated Domestic Equipment. The other excellent standard for defining the issue is EN 563:1994 Safety of machinery - Temperatures of touchable surfaces - Ergonomics data to establish temperature limit values for hot surfaces. The former standard has been used for many years in the UK by enforcement officers to pursue prosecutions, which is where I came across it. The latter standard is listed as a Machinery Directive document and it contains some really useful graphs of exposure time vs. temp. I refer to these regularly when testing equipment in-situ, especially laboratory and semiconductor manufacturing systems as many standards do not leave room for non-specified applications, or are vague. Your point about hot air streams is interesting and you may want to refer to the EN 60335 family of standards for guidance. As an ex-cooking product designer, the temperature of an air stream was not a regulatory requirement. It is difficult to measure accurately and hence was not called up in standards. It was an issue with respect to users, however. Alan _ Alan Brewster Compliance Certification Services 1366 Bordeaux Drive Sunnyvale, CA 94089-1005 Tel: 408-752-8166 ext. 122 Fax: 408-752-8168 e-mail: abrews...@ccsemc.com http://www.ccsemc.com -Original Message- From: Israel Yeshurun [SMTP:israel_yeshu...@stcl.scitex.com] Sent: Thursday, October 07, 1999 3:43 AM To: 'emc-p...@ieee.org' Subject: Hot Surface. Hot air. Dear Group Fellows I would like to raise the following two issues: 1) UL1950 / EN60950 Safety standards, Subclause 5.1 - Heating, Table 16 part 2, specify permissible temperature rise for external surfaces of equipment in Operator Access Area.. For external surfaces, made of metal which may be touched, it allows temperature rise of 45 degrees Kelvin, assuming ambient temperature of 25 degrees Celsius it allows surface temperature of 70 degrees Celsius = 158 degrees Fahrenheit ! Note (4) in this table applies to external surfaces that are not likely to be touched in normal use and measure less than 50 mm, in this case it allows a temperature rise of 75 degrees K, that under 25 degrees C ambient allows 100 degrees C = 212 degrees F !! Now, 70 degrees C for external equipment surface that may be touched seems pretty high to me. 100 degrees C metal surface will, I believe, cause a burn to that part of the human body that touched it. So maybe my interpretation is not true ??and, can someone point another regulatory source for Hot surface permissible temperature ? 2) Regarding Hot air flowing out of equipment, in UL1950 / EN60950 I could not find a requirement or limit for the maximum permissible temperature for it, Can someone point another regulatory source for Hot air permissible temperature ? Note: The equipment I relate to is ITE or Office, but information from Machinery standards or other sources is welcome ! Many Thanks Israel Yeshurun - This message is coming from the emc-pstc discussion list. To cancel your subscription, send mail to majord...@ieee.org with the single line: unsubscribe emc-pstc (without the quotes). For help, send mail to ed.pr...@cubic.com, jim_bac...@monarch.com, ri...@sdd.hp.com, or roger.volgst...@compaq.com (the list administrators). - This message is coming from the emc-pstc discussion list. To cancel your subscription, send mail to majord...@ieee.org with the single line: unsubscribe emc-pstc (without the quotes). For help, send mail to ed.pr...@cubic.com, jim_bac...@monarch.com, ri...@sdd.hp.com, or roger.volgst...@compaq.com (the list administrators).
Re: Hot Surface. Hot air.
I have a copy of a standard EN 563:1994, Safety of machinery - Temperatures of touchable surfaces - Ergonomics data to establish temperature limit values for hot surfaces. It is only 18 pages but includes charts and graphs of burn threshold vs contact time for plastic, metal, and ceramic materials. Patty Elliot Qualcomm, Inc. p...@qualcomm.com At 12:47 PM 10/7/99 -0400, Peter E. Perkins wrote: Here's a post from 1997... I don't know where I got the following chart, but I believe it's from the The Shriners Burn Institute. Someone else gave it to me. If anyone recognizes this list, I would really like to know. I assume I'm quoting someone, so I take absolutely no credit for it. TEMP | Time to deg.F | deg C | Serious Burn 120 49| over 5 min 125 52| 1-1/2 to 2 min 130 55| about 30 sec 135 57| about 10 sec 140 60| under 5 sec 145 63| under 3 sec 150 66| about 1-1/2 sec 155 68| about 1 sec - - - - - Peter E Perkins Principal Product Safety Consultant Tigard, ORe 97281-3427 +1/503/452-1201 phone/fax p.perk...@ieee.org email visit our website: http://ourworld.compuserve.com/homepages/peperkins - - - - - - This message is coming from the emc-pstc discussion list. To cancel your subscription, send mail to majord...@ieee.org with the single line: unsubscribe emc-pstc (without the quotes). For help, send mail to ed.pr...@cubic.com, jim_bac...@monarch.com, ri...@sdd.hp.com, or roger.volgst...@compaq.com (the list administrators).
RE: Hot Surface. Hot air.
One possible answer re the hot air issue: Whatever the surface is (metal grill, plastic vent slots, etc.) that the hot air is exiting the equipment from, will have to comply with the external temperature limits already cited. If the air itself is so hot that there is a burn hazard, those external surfaces will likely fail the temperature limit. Regards, Jim Eichner Senior Regulatory Compliance Engineer Statpower Technologies Corporation jeich...@statpower.com http://www.statpower.com Any opinions expressed are those of my invisible friend, who really exists. Honest. -Original Message- From: Israel Yeshurun [SMTP:israel_yeshu...@stcl.scitex.com] Sent: Thursday, October 07, 1999 3:43 AM To: 'emc-p...@ieee.org' Subject: Hot Surface. Hot air. Dear Group Fellows I would like to raise the following two issues: 1) UL1950 / EN60950 Safety standards, Subclause 5.1 - Heating, Table 16 part 2, specify permissible temperature rise for external surfaces of equipment in Operator Access Area.. For external surfaces, made of metal which may be touched, it allows temperature rise of 45 degrees Kelvin, assuming ambient temperature of 25 degrees Celsius it allows surface temperature of 70 degrees Celsius = 158 degrees Fahrenheit ! Note (4) in this table applies to external surfaces that are not likely to be touched in normal use and measure less than 50 mm, in this case it allows a temperature rise of 75 degrees K, that under 25 degrees C ambient allows 100 degrees C = 212 degrees F !! Now, 70 degrees C for external equipment surface that may be touched seems pretty high to me. 100 degrees C metal surface will, I believe, cause a burn to that part of the human body that touched it. So maybe my interpretation is not true ??and, can someone point another regulatory source for Hot surface permissible temperature ? 2) Regarding Hot air flowing out of equipment, in UL1950 / EN60950 I could not find a requirement or limit for the maximum permissible temperature for it, Can someone point another regulatory source for Hot air permissible temperature ? Note: The equipment I relate to is ITE or Office, but information from Machinery standards or other sources is welcome ! Many Thanks Israel Yeshurun - This message is coming from the emc-pstc discussion list. To cancel your subscription, send mail to majord...@ieee.org with the single line: unsubscribe emc-pstc (without the quotes). For help, send mail to ed.pr...@cubic.com, jim_bac...@monarch.com, ri...@sdd.hp.com, or roger.volgst...@compaq.com (the list administrators). - This message is coming from the emc-pstc discussion list. To cancel your subscription, send mail to majord...@ieee.org with the single line: unsubscribe emc-pstc (without the quotes). For help, send mail to ed.pr...@cubic.com, jim_bac...@monarch.com, ri...@sdd.hp.com, or roger.volgst...@compaq.com (the list administrators).
Hot Surface. Hot air.
Here's a post from 1997... I don't know where I got the following chart, but I believe it's from the The Shriners Burn Institute. Someone else gave it to me. If anyone recognizes this list, I would really like to know. I assume I'm quoting someone, so I take absolutely no credit for it. TEMP | Time to deg.F | deg C | Serious Burn 120 49| over 5 min 125 52| 1-1/2 to 2 min 130 55| about 30 sec 135 57| about 10 sec 140 60| under 5 sec 145 63| under 3 sec 150 66| about 1-1/2 sec 155 68| about 1 sec - - - - - Peter E Perkins Principal Product Safety Consultant Tigard, ORe 97281-3427 +1/503/452-1201 phone/fax p.perk...@ieee.org email visit our website: http://ourworld.compuserve.com/homepages/peperkins - - - - - - This message is coming from the emc-pstc discussion list. To cancel your subscription, send mail to majord...@ieee.org with the single line: unsubscribe emc-pstc (without the quotes). For help, send mail to ed.pr...@cubic.com, jim_bac...@monarch.com, ri...@sdd.hp.com, or roger.volgst...@compaq.com (the list administrators).
Re: Hot Surface. Hot air.
Hello Israel, I've not checked your numbers but believe the rationale is, in the case of Item 1) below: that should one come into contact with a surface at these temperatures, one will withdraw quickly and no damage is anticipated. And, in the case of Item 2) below: should one come into contact with this surface (even though unlikely one will withdraw even more quickly than in the above case; again, no damage is expected. Also, one can, and in some cases shall mark surfaces with the IEC symbol for Hot Surfaces (I don't have that symbol number at hand - sorry). Regards, Art Michael Int'l Product Safety News A.E. Michael, Editor P.O. Box 1561 INT Middletown CT 06457-8061 U.S.A. Phone : (860) 344-1651 Fax: (860) 346-9066 Email : i...@connix.com Website: http://www.safetylink.com ISSN : 1040-7529 -- On Thu, 7 Oct 1999, Israel Yeshurun wrote: Dear Group Fellows I would like to raise the following two issues: 1) UL1950 / EN60950 Safety standards, Subclause 5.1 - Heating, Table 16 part 2, specify permissible temperature rise for external surfaces of equipment in Operator Access Area.. For external surfaces, made of metal which may be touched, it allows temperature rise of 45 degrees Kelvin, assuming ambient temperature of 25 degrees Celsius it allows surface temperature of 70 degrees Celsius = 158 degrees Fahrenheit ! Note (4) in this table applies to external surfaces that are not likely to be touched in normal use and measure less than 50 mm, in this case it allows a temperature rise of 75 degrees K, that under 25 degrees C ambient allows 100 degrees C = 212 degrees F !! Now, 70 degrees C for external equipment surface that may be touched seems pretty high to me. 100 degrees C metal surface will, I believe, cause a burn to that part of the human body that touched it. So maybe my interpretation is not true ??and, can someone point another regulatory source for Hot surface permissible temperature ? 2) Regarding Hot air flowing out of equipment, in UL1950 / EN60950 I could not find a requirement or limit for the maximum permissible temperature for it, Can someone point another regulatory source for Hot air permissible temperature ? Note: The equipment I relate to is ITE or Office, but information from Machinery standards or other sources is welcome ! Many Thanks Israel Yeshurun - This message is coming from the emc-pstc discussion list. To cancel your subscription, send mail to majord...@ieee.org with the single line: unsubscribe emc-pstc (without the quotes). For help, send mail to ed.pr...@cubic.com, jim_bac...@monarch.com, ri...@sdd.hp.com, or roger.volgst...@compaq.com (the list administrators). - This message is coming from the emc-pstc discussion list. To cancel your subscription, send mail to majord...@ieee.org with the single line: unsubscribe emc-pstc (without the quotes). For help, send mail to ed.pr...@cubic.com, jim_bac...@monarch.com, ri...@sdd.hp.com, or roger.volgst...@compaq.com (the list administrators).
Hot Surface. Hot air.
Dear Group Fellows I would like to raise the following two issues: 1) UL1950 / EN60950 Safety standards, Subclause 5.1 - Heating, Table 16 part 2, specify permissible temperature rise for external surfaces of equipment in Operator Access Area.. For external surfaces, made of metal which may be touched, it allows temperature rise of 45 degrees Kelvin, assuming ambient temperature of 25 degrees Celsius it allows surface temperature of 70 degrees Celsius = 158 degrees Fahrenheit ! Note (4) in this table applies to external surfaces that are not likely to be touched in normal use and measure less than 50 mm, in this case it allows a temperature rise of 75 degrees K, that under 25 degrees C ambient allows 100 degrees C = 212 degrees F !! Now, 70 degrees C for external equipment surface that may be touched seems pretty high to me. 100 degrees C metal surface will, I believe, cause a burn to that part of the human body that touched it. So maybe my interpretation is not true ??and, can someone point another regulatory source for Hot surface permissible temperature ? 2) Regarding Hot air flowing out of equipment, in UL1950 / EN60950 I could not find a requirement or limit for the maximum permissible temperature for it, Can someone point another regulatory source for Hot air permissible temperature ? Note: The equipment I relate to is ITE or Office, but information from Machinery standards or other sources is welcome ! Many Thanks Israel Yeshurun - This message is coming from the emc-pstc discussion list. To cancel your subscription, send mail to majord...@ieee.org with the single line: unsubscribe emc-pstc (without the quotes). For help, send mail to ed.pr...@cubic.com, jim_bac...@monarch.com, ri...@sdd.hp.com, or roger.volgst...@compaq.com (the list administrators).
