I think in this case the guidance would say the boiler room needs a fire door.
However as the RP I would produce a written risk assessment in the normal way and if my liklihood / consequence analysis of risk did not give a clear indication one way or the other I would further analyse it by setting out the strengths ( whats good, risk control measures in place and proposed) , weaknesses ( ie variations from the benchmark standards, other weaknesses of the layout, nature or use of the building) , opportunities for improvement (What you could do, how much it would cost and any benefit in terms of the liklihood/ consequence) and threats ( ie what could go wrong or any consequences or action that may be taken if it did go wrong).
The SWOT analysis may help the RP to make up his mind over the level of risk that he feels is tolerable. We often find that organisations simply cannot afford to make all their premises compliant with the best practice guidance all at once, and advise them, through the assessment and SWOT, in respect of priorities for their limited funds. Sometimes it ends up as a 10 year plan.