Matched context for evacuation and back-flow

The page lists matched contexts for evacuation and back-flow.

Share - evacuation	Share - back-flow	Phrase
5.53%	18.94%	{evacuation or back-flow} valve
2.45%	27.51%	prevent {evacuation or back-flow} [perform operation]
3.38%	9.86%	fluid {evacuation or back-flow}
4.98%	4.08%	air {evacuation or back-flow}
2.80%	6.12%	gas {evacuation or back-flow}
2.14%	6.55%	fuel {evacuation or back-flow}