sentences:  In the US the Occupational Safety and Health Administration (OSHA) mandates engineered solutions to potential hazards, however silica sand continues to be allowed even though most commonly used blast helmets are not sufficiently effective at protecting the blast operator if ambient levels of dust exceed allowable limits.Adequate levels of respiratory protection for blast operations in the United States is approved by the National Institute for Occupational Safety and Health (NIOSH).Typical safety equipment for operators includes