Airborne Precautions

A surgical mask stops droplets, but tuberculosis particles float in the air for hours — if you walk into that room without the right respirator, standard PPE won't save you.

Airborne precautions target pathogens transmitted via tiny droplet nuclei (≤5 micrometers) that remain suspended in air and travel long distances. The three classic airborne diseases are tuberculosis (TB), measles (rubeola), and varicella (chickenpox) — remember "MTV." Disseminated herpes zoster also requires airborne precautions. The patient must be placed in an airborne infection isolation room (AIIR), which maintains negative pressure relative to the hallway, with a minimum of 6 air exchanges per hour (12 for new construction). The door stays closed at all times. Anyone entering wears an N95 respirator or powered air-purifying respirator (PAPR). An N95 must be fit-tested annually and seal-checked every time it is donned — a loose seal renders it useless. Visitors need instruction on proper respirator use before entering. The patient wears a surgical mask during transport outside the AIIR; transport should be limited to essential procedures only. Negative-pressure status is verified daily, often with a flutter strip or smoke test at the door.

Key Distinctions

Don't confuse airborne (≤5 μm, N95 required, negative-pressure room) with droplet (>5 μm, surgical mask sufficient, private room but no special ventilation). Students commonly think any respiratory illness needs an N95 — influenza and COVID-19 routine care use droplet precautions unless aerosol-generating procedures are performed. The patient wears a surgical mask during transport, not an N95; staff wear the N95 inside the room, not the patient.

Clinical Pearl

MTV needs negative air: Measles, TB, Varicella → N95 + negative-pressure room. If the room pressure isn't negative, the isolation isn't real.