Assessment of hydrogen sulfide emission levels on the floors of some selected bakeries in southwestern Nigeria

The hydrogen sulfide (H S) emission and oxygen (O2) level was measured within four bakeries in Ota, Ogun State. This was done to know the effect of H2S on the people working in bakeries and those walking into bakeries for business purposes. The data obtained was analyzed and the H 2 S emission level was around the new recommendation for airborne of 1 ppm recommended for 8 hours by ACGIH (American Conference Governmental Industrial Hygenist [1]. The highest mean concentrations of H2S were; bakery 1 (0.4 ppm), bakery 2 (0.73 ppm), bakery 3 (1.0ppm), H 2 S emission was not detected by the gas analyzer in bakery 4. O 2 level (20.8ppm) remained constant all through the study, which is the expected ambient O2 value, this is because of the cross ventilation within the bakeries. Though literatures have shown that ovens emit some harmful gases like CO, NO x , VOC and H 2 S, the concentrations of these gases can be reduced if there is cross ventilation within the bakery and exhaust stacks positioned high enough towards the roof, out of the building. The stack effect happens, when warm air moves or flow upwards in the building. The warm air rises because it is lighter than cold air, when it rises, it escapes out of the upper levels of the building through ventilation openings, windows or leakages. The rising warm air reduces the pressure at the base of the building, forcing cold air to infiltrate through either open doors, windows, or other openings and leakage in lower levels of the building. The H2S emission level was higher during the heating periods than the baking periods in all the bakeries considered due to the combustion process taking place during heating. The electrically fired ovens gave lower H 2 S concentrations than the wood fired ovens. To ensure safety for workers and consumers in Bakeries, regular inspection of bakeries should become a priority for the various agencies involved.