I know nothing of the process for a board house to gain UL approval. I can tell you alot about UL approvals from an OEM point of view. One of the criteria that UL approves all sorts of electronic devices is to restrict the size of holes in the bottom covers of products. If you need to violate the hole restriction with larger holes for say more air flow, UL allows you to provided a UL 94V-0 rated pc board is immediately over to hole or holes. Other areas that require UL 94V-0 rated boards is through customer contracts especially with the telcos. Some years back a central switching office for a major telco in the Chicago area burned down shutting service down for quite a while. They all have since become very sensitive to flammability issues. In some cases, they demand the OEM to go above and beyond what the standards require. It's rather humbling to sit across the table from a major telco customer trying to cut costs as best you can, only to be told to do so could jeopardize your own 911 call. They take this very seriously and they do not back down from it. The standards by which mfrs are required to make boards in my humble opinion are fairly robust. I've never had any problems over the past 17 years. When you require a certain flame rating for a board, you don't have to second guess it. ################################################################ TechNet E-Mail Forum provided as a free service by IPC using LISTSERV 1.8c ################################################################ To subscribe/unsubscribe, send a message to [log in to unmask] with following text in the body: To subscribe: SUBSCRIBE TechNet <your full name> To unsubscribe: SIGNOFF TechNet ################################################################ Please visit IPC's web site (http://www.ipc.org) "On-Line Services" section for additional information. For technical support contact Hugo Scaramuzza at [log in to unmask] or 847-509-9700 ext.312 ################################################################