I once worked as a Vertebrate Pest Control Adviser. It is a smell that keeps the animals away. That is how it works. They have to enter an area to smell the scent, of course. Scent repellents will not burn or injure an animal. Active Ingredients:

They are natural and organic: 1.15% Rosemary Oil, 0.31% Cinnamon Oil, 1.15% Peppermint Oil, 1.53% Putrescent Whole Egg Solids

You should be happy your landlord is using scent based repellents, instead of poison baits, such as rat poison! Scented repellents is a safe way to exclude rodents, with out harming them. The internet can also be a source of misinformation, use caution when quoting it.