18-28-502.8.6.2 Open and closed systems.
   Mechanical exhaust ventilation shall be provided for highly toxic and toxic liquids used in open systems in accordance with Section 18-28-502.7.4. Mechanical exhaust ventilation shall be provided for highly toxic and toxic liquids used in closed systems in accordance with Section 18-28-502.7.5.
   Exception: Liquids or solids that do not generate highly toxic or toxic fumes, mists or vapors.