In many cases of rat infestations, one of the first indications that there is a problem is the presence of rat urine and faeces. But, whereas rat droppings are relatively easy to spot, detecting their urine can be more difficult. Unless there’s a significant amount of it, you are unlikely to smell it. An individual rat won’t produce enough urine for people to detect unless you happen to be nearby when the urine is fresh. If you do smell rat urine, it’s more likely because you have multiple rats nesting in your home.
Like the urine of other rodents, rat urine has a strong ammonia-like smell. Rat urine is brimming with nitrogen. As the nitrogen breaks down in the presence of oxygen, it forms ammonia, which has a strong odour. It also leaves behind a chalky residue when it dries because of its high calcium content. Some people describe the smell of stale rat urine as ‘musky’.
If you think you can smell rat urine, you need to immediately confirm whether you have an infestation. You should also thoroughly clean any surfaces rats have urinated on; their urine can spread all manner of nasty diseases you want to stay well clear of. You can remove rat urine stains by combining vinegar and water in a solution of four parts vinegar to one part water. Spray this on affected surfaces and leave it for an hour before wiping it away with plain water.
You can confirm the presence of rat urine using UV light. Rat urine glows brightly under UV light, making it an effective way of searching for trails near potential entry points rats might use to get into your home. Similarly, you can use UV light to search for a urine trail leading from rat droppings back to the rat’s nesting spot.