Background: Adoption of voluntary smoking restrictions continues to increase in US private households and the hospitality industry. Unfortunately, discrepancies regarding their scope, implementation, and enforcement exist, potentially compromising their impact on lowering nonsmokers' exposure to tobacco smoke toxicants. The objective of this dissertation was to examine the role of voluntary smoking restrictions on reducing secondhand smoke (SHS) and thirdhand smoke (THS) exposure of nonsmokers in private settings. Methods: Data for this dissertation were taken from three separate existing studies conducted in San Diego, CA, examining (1) SHS exposure among pre-teens (Chapter 2, N=388 families), (2) THS pollution of private homes (Chapter 3, N=100 homes), and (3) smoking policy of rental car companies (Chapter 4, N=6 national companies with N=125 local branches). Data for Chapter 2 were examined using multinomial logistic regression to examine the circumstances under which parent/child dyads agreed on a smoking ban. Data for Chapter 3 were examined using multinomial logistic regression to investigate the role of smoking restrictions and behaviors on THS pollutants in dust and on surfaces. Data for Chapter 4 were examined to describe smoking policies at the corporate level and explore their implementation in local branches. Results: In Chapter 2, 18.3% of dyads disagreed on the presence of a complete smoking ban. Factors that contributed to this disagreement included residents' smoking behaviors and parents inconsistently asking visitors to smoke outside. In Chapter 3, home smoking rules and compliance with rules were found to affect indoor smoking rates, which in turn influenced THS contamination in dust and on surface. Other factors that impacted THS in dust were home features and remediation efforts. In Chapter 4, four of the six national rental car companies reported an official smoking policy. Lack of training and communication to local branch staff resulted in poor implementation of the official company smoking policies and failure to protect customers from THS exposure. Discussion: Private indoor settings remain the primary location for exposure to tobacco smoke pollutants for nonsmokers. Voluntary smoking restrictions in private settings can reduce THS contamination and exposure. Residents and management need to define, communicate, and consistently implement smoking restrictions to ensure a true smoke-free environment.