Wash all clothes and blankets in the house. Smell them as they come out of the dryer to ensure nothing has a urine smell.
Do a thorough apartment cleaning for all hard surfaces. Sweep and mop the floors and wipe down counters and tile with nontoxic cleaning agents. If the nonporous surfaces are cleaned and the urine smell persists, it means the urine has stained a soft material such as carpet, a rug or couch.
Turn off all the lights in your apartment and turn the hand-held black light on. Scan rugs, carpet, couches or seat cushions. Urine will fluoresce under the black light. Smell any potential problem areas and mark spots that smell of urine.
Use an even mixture of water and white vinegar on recent urine spots. Pour the mixture on top of the area, then dab the area with just water. Press a bath towel on top until dry, then leave another thick bath towel over the spot overnight.
Apply an enzyme cleaner to older urine stains, or areas where the pet has urinated repeatedly. Follow the directions on the bottle; most require that you dose the carpet or fabric in the cleaning agent and allow to dry. Once the liquid dries, vacuum over the cleaned area.
Open any doors or Windows in your apartment and allow 24 hours for the smells to air out.