Under Cal/OSHA regulations on respirable crystalline silica, what dust control measure is required when shot-blasting or grinding concrete pavement prior to striping?

1. Open windows and rely on natural wind currents to blow dust away.
2. Use tools equipped with HEPA-filtered dust collection or wet suppression.
3. Instruct workers to hold their breath while operating grinding equipment.
4. Sweep dry concrete dust with a standard straw push broom into pile.