The speed of the fan is dependent on the temperature of the graphic card so it varies from card tocard but no fan can go below 40% of the speed at any cost and for maximum it may be using 100% if the card is heating up.
I run my 9800gt card at 100% all the time to get the best cooling of the card though this is not recommended.
If you don't tinker around with the timing of the card or the voltages and the fan speed settings and leave everything at their defaults, then you will not end up burning anything. It works absolutely fine at company settings.
I wouldn't worry too much , unless you live in a place with high ambient temps.