Transmission-based precautions are added on top of standard precautions when a patient is known or suspected to carry an organism that spreads by a specific route. There are three categories, contact, droplet, and airborne, and each maps to a particular PPE set and room type. The RN's job is to recognize the likely route early, often before a culture confirms it, and to implement the right precautions promptly so the unit is protected while diagnostics are pending. The categories exist because organisms travel differently. Some ride on hands and surfaces, some on large respiratory droplets that fall within a few feet, and some on tiny droplet nuclei that stay suspended and travel on air currents. Matching the barrier to the route is what actually stops spread. Picture the decision in practice: you are the nurse admitting a client with a new productive cough, night sweats, and weight loss. Which action takes priority? Anticipating airborne tuberculosis, you place the client in an airborne infection isolation room and don an N95 before a definitive diagnosis, because waiting for confirmation would expose staff...