The decision of what coolant to use attracted more debate. The Metallurgical laboratory's first choice was helium, because it could be both a coolant and a neutron moderator. The difficulties of its use were not overlooked. Large quantities would be required, and it would have to be very pure, with no neutron-absorbing impurities. Special blowers would be required to circulate the gas through the reactor, and the problem of leakage of radioactive gases would have to be solved. None of these problems were regarded as insurmountable. The decision to use helium was conveyed to DuPont, the company responsible for building the production reactors, and was initially accepted.