Perhaps you should try some spelling variations:
"5 ppm decrease" » "5 a decrease" (Expand Search), "5 pa decreased" (Expand Search), "5 026 decrease" (Expand Search)
"5 non decrease" » "5 point decrease" (Expand Search), "5 note decreased" (Expand Search), "5 fold decrease" (Expand Search), "_ non decrease" (Expand Search), "a non decrease" (Expand Search), "e non decrease" (Expand Search)
"5 nn decrease" » "5 a decrease" (Expand Search), "5 mean decrease" (Expand Search), "5 gy decreased" (Expand Search), "59 nn decrease" (Expand Search), "5 nm decrease" (Expand Search), "5 n decrease" (Expand Search)

You may be able to get more results by adjusting your search query.

• The words AND, OR and NOT may confuse the search; try adding quotes: "((((\"5 ppm decrease\") OR (\"5 _ decrease\"))) OR (((\"5 nn decrease\") OR (\"5 non decrease\"))))~".
• Removing quotes may allow a broader search: (((( 5 ppm decrease ) OR ( 5 _ decrease ))) OR ((( 5 nn decrease ) OR ( 5 non decrease ))))~.
• Adding a wildcard symbol may retrieve word variants: (((("5 ppm decrease") OR ("5 _ decrease"))) OR ((("5 nn decrease") OR ("5 non decrease"))))*.