In heat waves, chemicals like formaldehyde and ozone can form more readily in the air, according to researchers driving mobile labs in New York City this week. In heat waves, chemicals like formaldehyde and ozone can form more readily in the air, according to researchers driving mobile labs in New York City this week. Global Warming, Greenhouse Gas Emissions, Air Pollution, Heat and Heat Waves, Hazardous and Toxic Substances, Research, Ozone, New York City, New Jersey NYT > Science