Is it permissible to perform tayammum for prayer if the workplace does not allow for wudu, and what is the correct method for tayammum?

Purity is a condition for the validity of prayer, and ablution (wudu') is the prescribed purification. Dry ablution (tayammum) is a substitute for it in case water is unavailable or one is unable to use it. What the questioner mentioned about not being allowed to use water for ablution is not one of the permissible reasons for tayammum. He should clarify the nature of the inability to use water. If there is a restroom with a basin for washing, he can perform ablution there. If that is not available, then he should go to work having already performed ablution. It is not permissible to perform tayammum when one is able to obtain and use water. If it is a woman, she must demand a private restroom, or seek alternative employment if the situation becomes too difficult.