Exhaled CO2-based tracer gas for measuring ventilation rates and energy consumption with application to worship places

Using the tracer gas technique, ventilation rates were estimated in an air-conditioned mosque located in Bahrain. Exhaled CO2 concentrations were traced for different occupancy levels and periods, i.e., 20–200 worshippers during ½ h, 1-h, and 2-h periods. The three known methods of tracer gas technique, namely build-up, steady-state, and decay methods, were examined with reference to measured ventilation rates. In addition to investigating the impact of ventilation rates and operating schedules on the cooling energy consumed. A ½ h occupancy showed a poor correlation between exhaled CO2 concentration and occupancy level, which means it misleads estimating ventilation rates in mosques. In contrast, the 1-h and 2-h occupancy periods showed a strong correlation. The steady-state method overestimated ventilation rates by 10%, while the build-up and decay methods showed 58% and 68%, respectively. Using the 5-prayers operating schedule instead of the on-24-hours schedule reduced the cooling energy consumed by 8%