Cooking is a major factor that affects the quality of indoor air especially in kitchens. It is a daily activity essential for supplying the requisite energy and nutrients for living through food consumption. Exposure to air pollutants from cooking with solid fuels in domestic and commercial kitchens is a leading health risk in developing nations like Ghana. Real-time monitoring of gaseous pollutants (CO, SO2, NO2) was done during eight hours of occupational cooking in different cookstove kitchens of 14 Senior High Schools in the Kumasi Metropolis, Ghana. The traditional and improved cookstove kitchens were fueled by firewood whereas the briquette cookstove kitchens were fueled by palm kernel shell briquette. The observed median concentrations in the kitchens were 0.43–39.44 mg m−3 for CO, 0.07–0.36 mg m−3 for NO2, and 0.19–0.61 mg m−3 for SO2. The concentrations in the traditional and briquette cookstove kitchens exceeded the respective World Health Organization (WHO) thresholds of 4 mg m−3 for CO, 0.025 mg m−3 for NO2, and 0.04 mg m−3 for SO2 mg m−3. The air quality index of traditional cookstove kitchens was classified as hazardous for human occupancy. Hazard indices > 1 revealed the likelihood of significant non-carcinogenic health risks for cooks’ occupational exposure to gaseous pollutants in all the cookstove kitchens. This study is essential as it informs on gaseous air quality during large-scale cooking within institutional kitchens with different cookstove types in a developing country. The study fills a gap in literature by providing real-time concentrations of gaseous air pollutants to which cooks in high school kitchens of a developing country are occupationally exposed. The study recommends the urgent transition of large-scale kitchens in developing countries to cleaner energies and cookstove types, alongside regular monitoring and enforcement of air quality guidelines, to safeguard occupational health.