Please look at this sentence. <br/><br/>"Special gear is needed when working with dangerous chemicals." <br/><br/>I want to change this sentence with using one among prepositions like at,in,on,for and so on.<br/><br/>"Special gear is needed in working with dangerous chemicals." Is this sentence okay? If not, couldn't you change it with using a preposition ? <br/><br/>Thanks in advance.