Definition - What does Airlock mean?
An airlock is an important tool utilized on the fermentation tank or holding vat in order to keep out undesirable micro-organisms. It also prevents oxygen from entering into the wine. The airlock is a necessity especially during fermentation as yeast does not produce alcohol until it is deprived of oxygen.
WineFrog explains Airlock
The airlock works as a one-way valve. When used during fermentation it allows for gases, such as carbon dioxide to escape. This one-way valve is an important tool to be used during all fermentations of wine in order to keep out unwanted bacteria such as VA, lactic bacteria and wild yeasts.
When using an airlock it is important to clean and sanitize it before and after use. It must only be filled with clean water and it should be checked to see that it is functioning on a daily basis.