- EPCO recommends using only porcelain lamp holder(s) for poultry farming applications. The lamp holder must be installed in a manner that will not permit dust or moisture to enter the junction box. In addition, the porcelain lamp holder must be mounted vertically with the lamp positioned below the lamp holder on a watertight , Dust Tight non-metallic junction box with an effective gasket between the junction box and the lamp holder as shown in the photo to the right.