If you buy a quality fan from a reputable seller and have had all the necessary manufacturer testing, then a dog crate cooling fan is safe to use with your pet.
But, as with all other electrical items or devices with moving parts, you should use the cooling fan carefully. And that means putting it in a place that won’t endanger your pet or so close that they can tip or knock it over. And never use it near water, which includes their drinking bowl. Finally, always follow the manufacturer’s user instructions.