Yes of course you can - you can issue this as a Project Manager instruction. You just will have to accept that assuming this was not a requirement in their original Works Information, this will then be a compensation event to the Contractor. Any additional cost and time implications that the additional fire requirements bring will be assessed as part of the CE quotation.
If this was a requirement that WAS in the Works Information and you think they missed it, you can instruct them to do it but it will NOT be a compensation event as you are instructing something that was already a requirement in the original WI.
If this was a requirement that WAS in the Works Information and you think they missed it, you can instruct them to do it but it will NOT be a compensation event as you are instructing something that was already a requirement in the original WI.