Why do high concentrations of hydrogen sulfide ($H_2S$) and carbon dioxide ($CO_2$) in poorly ventilated winter sheds increase chick mortality?

During winter brooding in cold regions like Quetta and Peshawar, farmers seal houses to conserve heat from coal or gas brooders. However, organic manure decay releases hydrogen sulfide ($H_2S$) and ammonia ($NH_3$), while gas combustion releases massive volumes of carbon dioxide ($CO_2$). Because $H_2S$ and $CO_2$ are heavier than air, they sink to the floor level—precisely where the 1-day-old chicks live. High $CO_2$ (above 3,000 ppm) induces respiratory acidosis, metabolic depression, and suffocation. $H_2S$, even at low concentrations (above 10 ppm), is highly toxic, paralyzing the cilia in the respiratory tract and preventing the clearance of dust and bacteria, leading to rapid E. coli infections and mortality. Implementing automated minimum ventilation on a cycle timer is mandatory to exchange air without dropping temperature. Farmers can read toxic gas thresholds in the Poultry Encyclopedia, buy multi-gas detectors and heaters on Poultry Plaza, monitor daily chick prices on Poultry Rates, and trade on Murghi Mandi.