The ONA Block is a fast easy way to fight odors at their source. This is a semi-solid block of counteractant which can be placed around where ever odors lurk. Remove the top or poke holes in it to release the agent as required. The blocks can be placed directly in ventilation ducting to neutralize undesirable odors as they are evacuated. Each block lasts 15 to 30 days. Simply open the lid and place in room or vents. The duration of the ona block will vary from 15 – 30 days relative to the airflow around the block and the ambient temperature. To limit the amount of odor control and extend block life poke holes in the cover and replace on the container.