I work in a chicken factory. I cannot pray Thuhr at work due to my dirty clothes which will be full with blood and chicken waste.
Can I join Thuhr with ‘Asr

All perfect praise be to Allah, The Lord of the Worlds. I testify that there is none worthy of worship except Allah, and that Muhammad is His slave and Messenger.

Dear brother,

Firstly, you should fear Allah and perform all the prayers at their prescribed fixed times. Allah Says (what means): {And whoever fears Allah - He will make for him a way out. And will provide for him from where he does not expect.} [Quran 65:2-3]

Secondly, we advise you to provide yourself with a clean garment that you keep in the factory where you work and whenever the time of prayer comes you clean any blood that might be stuck to your body, perform ablution, and then wear your clean garment and pray. But if you cannot do what we suggested, or if you find it difficult to apply it, then you can join Thuhr with ‘Asr. There are two forms of joining the prayers:

First the artificial combining: It consists of praying Thuhr in the last period of its fixed time; i.e., just enough time to pray four Rak’as before the beginning of the time of ‘Asr prayer. In this case, the person prays both Thuhr and ‘Asr at their fixed times.

The second form is the effective joining: It consists of delaying Thuhr prayer till its fixed time expires then joining it with ‘Asr, in what is called delayed Thuhr prayer. This last form of joining should not be done except when there is a real necessity to do so.

However, joining prayers should not become a habit. In fact, the joining of two prayers should be an exception as narrated in the sound Hadeeth by Al-Bukhari and Muslim from Ibn ‘Abbas that he said: “The Prophet combined his prayer because he did not want to put his Ummah (nation) to hardship, and it was not because of illness or any other reason.”

The Hadeeth from Ibn 'Abbas was reported by Imam Muslim who said: “The Prophet combined the Thuhr and ‘Asr and then the Maghrib and 'Isha in Madeenah without the existence of any danger or rain.”

Ibn 'Abbas was asked: “What did he intend by that action?” He replied: “He did not want any hardship for his Ummah.” [Al-Bukhari and Muslim]

Allah knows best.