1. 29 C.F.R., 1910.146, 1993. OSHA, Permit-required Confined Spaces for General Industry. U.S. Department of Labor.
2. American Conference of Governmental Industrial Hygienists (ACGIH), 2013. TLVs and BEIs. Threshold Limit Values for Chemical Substances and Physical Agents & Biological Exposure Indices. ACGIH, Cincinnati, OH.
3. American Industrial Hygiene Association (AIHA), 2014. Prevention Through Design: Eliminating Confined Spaces and Minimizing Hazards. AIHA, Falls church, VA.
4. American National Standards Institute (ANSI), American Society of Safety Engineers (ASSE), 2009. Safety Requirements for Confined Spaces (ANSI/ASSE: Z117.1-2009). ANSI, Washington D.C.
5. American National Standards Institute (ANSI), American Society of Safety Engineers (ASSE), 2011a. Prevention Through Design: Guidelines for Addressing Occupational Hazards and Risks in Design and Redesign Processes (ANSI/ASSE: Z590.3-2011). ANSI, Washington D.C.