How Minimum Ventilation Works and Why It Controls Moisture

During cold weather or early brooding stages, minimum ventilation fans are not run to cool the birds. Their primary purpose is to remove respiratory and drinker moisture while bringing in oxygen and diluting harmful gases like ammonia and carbon dioxide.

Cold outside air holds very little absolute water mass, even if its relative humidity (RH) is high. When this cold air enters a heated poultry house, it warms up. As air warms, its moisture-holding capacity expands exponentially: every 20°F rise in air temperature approximately doubles its capacity to hold water vapor. This warm air acts like a sponge, drawing moisture out of the wood shavings or built-up litter before being exhausted by timer-controlled fans.

Why 50-60% Relative Humidity Is the Target

Keeping the house between 50% and 60% RH is critical for poultry welfare and productivity. If relative humidity drops below 40%, the air becomes too dry and dusty, causing respiratory irritation in young chicks. Conversely, if relative humidity exceeds 60-70%, the litter will begin to seal over and slick. Wet litter releases harmful ammonia, increases paw lesions (pododermatitis), reduces bird weights, and raises heating costs because evaporating floor water absorbs energy that should be heating the birds.