Indoor-outdoor carbon monoxide concentrations at four sites in Riyadh, Saudi Arabia.

In Saudi Arabia, the major outdoor anthropogenic source of carbon monoxide (CO) is the 4,280,986 cars registered in the Kingdom last year. Of these vehicles, approximately 1,300,000 are registered in the Riyadh area. The major sources of indoor CO in Riyadh are gas cooking facilities, kerosene heaters, charcoal burners, hubble bubble pipes (water pipes), and tobacco smoking. The current Saudi Arabian Ambient Air Quality Standards (SAAQS) for CO are 10 mg/m{sup 3} (9 ppm) maximum for 8-hour average exposure, and 40 mg/m{sup 3} (35 ppm) for 1-hour average exposure. The allowable exceedance is twice per month. These standards are the same for the United States except no exceedance is allowed. The objective of this study was to evaluate the CO levels indoors and outdoors at four sites in Riyadh. Continuous sampling was conducted at four sites with Ecolyzer Series 200 Monitors, together with Rustrak Recorders Model 288.