Like the name suggests, Odour Neutralising Agent (ONA) Blocks and Gel are a great way of combating unwanted smells.
Available as either gel or block and in a choice of fragrances, ONA has a wide variety of application and places where it can be used.
The ONA Block is a low-cost way of managing smells and can also be used by drilling a few holes in the lid to extend its lifespan. Some people have also found that by breaking it out of the pot it is possible to smear it inside ductwork and boost the effects of a carbon filter.
The gel can also be used by placing small amounts in various places to maximise the surface area and avoid the crust that can form at the top of an open jar.
It can also be incorporated into ducting by using a T-Piece and, if needed, a ducting reducer (the one litre gels are nearly a perfect fit for a four-inch/100mm reducer).
Estimating the lifespan of the ONAs is hard as much will depend on airflow, humidity and temperature, but an average would be four to six weeks for the ONA Block and ONA Gel 1L.