Improve search engine criteria

When doing advanced search for products with certain criteria, the search engine will only show results if all criteria are met.

E.g., if I want to do a product search based on certain CLP-lables, products that meet only a few of those, will not be shown. It seems to me like the search engine criteria is based on an "and" function instead of an "or"-function.

It would be nice to do only one search and get results even if only some criteria are met, instead of doing several searches, all with different criteria. The latter would give many duplicated results.