Major reasons that engineering controls alone are not enough to protect workers from respirable crystalline silica
- Respirable crystalline silica is nearly as light as air and has a very slow "settling rate"...it takes a long time to drift to the ground.
- Because of the low settling rate, respirable crystalline silica can't be completely contained and is impossible to eradicate
- NIOSH and the silica sand mining industry have spent five decades trying to perfect engineering and administrative controls, and yet the respirable crystalline silica conditions still persist.
- Due to the highly abrasive nature of crystalline silica (remember, it's used for sand paper and sandblasting), engineering control equipment continues to break down, escalating the release of respirable dust and increasing maintenance costs.
- The new respirable crystalline silica rule proposed by OSHA emphasizes that engineering controls should always be used in combination with work practices (worker hygiene, clothes cleaning, PPE, etc).