A successful pitstop takes between fourteen to sixteen seconds to change four tires and add 22 gallons of fuel. Indeed, when rushing, mistakes sometimes do happen to increase this time interval. With cars moving at nearly 200mph, just one second makes a huge difference concerning postioning on the track. Races can be won and lost in the pits, with the last pitstop possibly becoming a "decisive moment".
This picture shows the car accelerating out of the pits immediately following refeuling, hence the smoke and the crew members still holding the gas cans. Pit crew members have a tough job and this photo is dedicated to them.