A rating system that measures a product's (often a luminaire's) resistance to environmental factors (primarily dust and moisture).
From http://www.sensorsone.co.uk/ip-rating-checker.html , we see that an IP65-rated fixture is impervious to "Total dust ingress protection" and "low pressure water jets from any direction".
From http://www.sensorsone.co.uk/ip-rating-checker.html , we see that an IP65-rated fixture is impervious to "Total dust ingress protection" and "low pressure water jets from any direction".