"Chlorine" . "Oxidizing agents" . "Hazardous air pollutants" . "Gases with color" . "Chemical elements" . "Pulmonary agents" . "Reactive nonmetals" . "Occupational safety and health" . "World Health Organization essential medicines" . "Swimming pool equipment" . "Diatomic nonmetals" . "WikiProject Elements pages using ENGVAR" . "Industrial gases" . "Halogens" .