A citizen project that tried to measure this found high but not alarming levels in NYC subways: https://medium.com/age-of-awareness/air-quality-in-the-nyc-subwa

A citizen project that tried to measure this found high but not alarming levels in NYC subways: https://medium.com/age-of-awareness/air-quality-in-the-nyc-subway-worse-than-you-might-think-285452679646 https://medium.com/age-of-awareness/air-quality-in-the-nyc-s... Yet another reason to wear high quality N95 masks in the future when on public transit.