Source control is the most effective layer: scoop promptly, right-size and place the boxes well, and keep ventilation open. It solves most odour complaints.

Physical adsorption relies on activated carbon, zeolite or deodorising beads around the box. The effect is modest but gentle, and the media needs regular replacement.

Fragrance masking presses strong scent over the smell. It feels effective short term but can make cats avoid the box and can hide signs of illness.

If odour suddenly worsens or comes with frequent urination, check for urinary problems rather than adding more deodoriser.