Based on these descriptions and the Byzantine sources, John Haldon and Maurice Byrne designed a hypothetical apparatus as consisting of three main components: a bronze pump, which was used to pressurize the oil; a brazier, used to heat the oil (πρόπυρον, "propyron", "pre-heater"); and the nozzle, which was covered in bronze and mounted on a swivel (στρεπτόν, "strepton"). The brazier, burning a match of linen or flax that produced intense heat and the characteristic thick smoke, was used to heat oil and the other ingredients in an airtight tank above it, a process that also helped to dissolve the resins into a fluid mixture. The substance was pressurized by the heat and the usage of a force pump. After it had reached the proper pressure, a valve connecting the tank with the swivel was opened and the mixture was discharged from its end, being ignited at its mouth by some source of flame. The intense heat of the flame made necessary the presence of heat shields made of iron (βουκόλια, "boukolia"), which are attested in the fleet inventories.