sulfuric acid won’t evaporate, but is hygroscopic and will draw water from the air. It won’t ‘turn to powder’ 98-99% H2SO4 that is readily purchased is in a liquid form. I think it will gradually release oxides of sulfur fumes (SO3), especially when heated, but these fumes will combine with water (like in your eyes and nose) and become acid again.
It won’t just go away. It will corrode whatever it can and turn to sulfates; or it will sit there collecting water turning to a bigger puddle of vile. Its better to ventilate well and add a neutralizing agent like baking soda