Simply replace the unfilled areas such as "__" and "_[date]_" with your information.
Dear _[supervisor or human resources rep]_,
Please accept this correspondence as a formal complaint regarding the state of _[list the working condition that is unsatisfactory here]_. This is creating a completed unacceptable working environment, and I feel that it is causing _[list health hazard or other negative effects of working condition]_.
I feel that productivity of all employees would be greatly improved if this issue was addressed. When working in conditions that cause negative feelings, employees will naturally be less willing to produce work. Also, the negative conditions are causing a lot of discussion among the staff, which is also leading to a decline in productivity.
Thank you in advance for your quick attention to this matter.