Prolonged Heat Exposure
Your MacBook Air may become very warm during normal use.
It’s important to keep your MacBook Air on a hard, stable, and well-ventilated work surface when in use or charging. 
Use common sense to avoid situations where your body is in prolonged contact with the device or its power adapter when it’s operating or plugged into a power source, as sustained contact with warm surfaces may cause discomfort or injury. 
Take special care if you have a physical condition that affects your ability to detect heat against the body.