It is permissible for shift workers

Q 6: There are some who sleep without having the intention of waking up when Salah becomes due time. They may even not wait for the time of Salah. They say: If we awaken during the time of Zhuhr (Noon) Prayer, we perform it and `Asr (Afternoon) Prayer at the time of Zhuhr Prayer, and if we awaken by the time of `Asr Prayer, we perform Zhuhr Prayer with it. What is the ruling in this case?

A 6: If they are traveling, then there is nothing wrong with combining prayers. However, if they are not on a journey, they should not do that as previously clarified in the fifth question.