In each city, research teams selleck chemicals were trained in the study procedures and testing methods by the principal investigator. Establishments were visited during the work shift with higher customer occupancy as reported by the manager. When available, one smoking and one nonsmoking area were selected for monitoring. Monitors were placed at the center of each designated area away from direct sources of ventilation, at least 50 cm away from any object that could block natural ventilation. Monitors were hung at a standard 2.3 m above the ground to avoid monitor loss or damage. Pilot studies were conducted to assure that monitors placed at 2.3 m reflected concentrations measured at respiratory height (1.6 m). Quality controls consisted of 10% duplicate monitors and 10% blank monitors.

Restaurants and bars have days and hours of no activity, so, to avoid previous dilution effects observed in approaches using weeklong monitoring (Barrientos-Gutierrez, Vald��s-Salgado, Reynales-Shigematsu, Navas-Acien, & Lazcano Ponce, 2007), nicotine was monitored for the duration of the work shift with higher customer occupancy (mean monitoring time equals 8.5 hr, SD equals 2.2 hr). Then, all monitors were taken to a laboratory, disassembled, and their filters were placed in individual vials to be refrigerated at 3.3 ��C until analyzed. Monitors were analyzed using a nitrogen-selective chromatograph according to standard protocols (Hammond & Leaderer, 1987). Detected nicotine was blank corrected and divided by the total volume of monitored air to obtain micrograms per cubic meter units.

The limit of detection (LOD) was 0.03 ��g/m3; concentrations under this level were imputed as half of the LOD. Establishment Characteristics Managers completed a questionnaire on the physical characteristics of their establishment. Information on type of establishment (bar or restaurant) obtained using the official census was corroborated or corrected using the manager��s report. Maximum occupancy was expressed as the maximum number of customers allowed in the establishment according to the establishment license. A walk-through was conducted to measure the establishment size with a digital laser distance meter and was categorized as ��100 or >100 m2. The manager questionnaire also asked about customer��s mean age, percent male customers, and neighborhood socioeconomic status (SES) on a scale from 1 (the poorest) to 10 (the richest).

We grouped scores 1�C4 as low SES, 5�C7 as medium SES, and 8�C10 as high SES. Mechanical Systems All mechanical systems designed to extract, ventilate, or mobilize air, independently of whether they were installed in response to SHS concentrations or because of other reasons, were considered ��mechanical systems.�� Information on mechanical systems was obtained from the manager��s Carfilzomib questionnaire.