It depends ...... what you are commissioning and constructing at the same time

If you could give more information, it would help.

You might need to think a bit deeper than that, again depending upon what you are doing.

Are any control systems affected - partially installed/commissioned etc e.g. only some parts work corectly - yet other may think the whole system is working.

Similarly emergency systems/alarms - fire alarms being the obvious. If process related systems you are commissioning - again system alarms, process isolations, knowledge of the current system status at all times if loss of containment could happen?

SUggest you need to complete a HAZID study/risk assessment for the various stages of the work.

Any SIMOPS carried out generally carries a higher degree of risk. Put construction workers next to any process operatons and you really need to have good robust control measures in place such as:

Process safety induction for all construction workers required to work in a pre-commissioning/commissioning areas
Access control to prevent unauthorised entry into pre-commissioning/commissioning areas
Robust PTW procedure which must be signed off by competent persons from both construction and commissioning signature authorities.
A plant/site specific SIMOPS plan which has been circulated and understood by all parties

Education and understanding is key. Construction workers do not generally understand the concept of process safety and there is always the risk of something they perceive to be very straighforward and normal such as grinding (hot works) can have such a devastating effect to a live or partially live plant.