You'll need to blow the air outside or draw it out.... the water saturated air has to go someone or you'll just be putting them into a sauna. Thats why i would be using a humidity controlled fan.we used a drying cupboard in our fire station to dry our fire kit between fires.
It may be different in NI, but in the UK mainland, Oftec have no legal powers over the end user / customer, only the installers. Installers can self-certify the work they carry out, but it isn't hard to find an installer who will ignore Oftec, although it is at their risk. Oil tank location and tank size is controlled by Building Regs and the Environment Agency. It is these that control whether bunding is necessary or not. However, existing installations are effectively exempt unless new work or replacements are required.
Oil theft and leaks are a big issue around London. There are plenty of places within the M25 that off grid.
Hence i said should meet oftec standards, also should be completed to local building control regulations, either way if not as an installer your leaving yourself wide open to legal action if anything goes wrong and youv cut corners.
Very few installations wouldnt require bunding due to risk of contamination to drains and open water etc .
