But, despite the open nature of a cruise ship, the air passengers breathe in may not be as clean as you think. A recent US study suggests that the air on cruise ship decks could potentially be as polluted and harmful as that in large, industrial cities such as Beijing.

In 2026, the air on a cruise ship is often cleaner than the air in many major cities, thanks to massive investments in Advanced Air Quality Systems (AAQS) and HEPA filtration. Modern ships use "scrubbers" that remove 98% of sulfur and 60–90% of particulate matter from the engine exhaust before it ever leaves the funnel. Inside the guest areas, the air is frequently "refreshed" with 100% outside air rather than being purely recirculated. In 2026, many premium cabins and public spaces are equipped with HEPA filters similar to those used in hospitals and airplanes, which can trap 99.97% of airborne pathogens, including viruses and bacteria. However, travelers should be aware of "stack gas" (exhaust) on the upper aft decks if the wind is blowing in a certain direction. While the industry has made leaps in reducing "smog-forming" emissions, the air quality is best on the forward decks or mid-ship balconies where you are constantly receiving fresh, ionized ocean air directly from the sea.