VOCs are 'Volatile Organic Compounds', meaning they are compounds containing carbon and are generally a gas at room temperature. Indoor VOCs can come from a range of activities, such as spraying perfumes or hair sprays, painting or cleaning.
When you see VOC on your machine's monitor or in your MyDyson app, you're experiencing a rise in VOCs, and your machine is working hard to remove the pollutant from the air, and project cleaned air into your home.