If you are using the drop-tube method, the best way is to use a vacuum pump (available from OCLS) which delivers the oil straight into the sample bottle! However, there will be some units which don’t allow such a method. In this case, some investigative work may be required to search for a suitable location. Also, there’s the option of contacting the unit manufacturer or browsing the Internet.
Full instructions are available on request from OCLS regarding the proper method for sample taking.