Chinese companies have improved the sterilization method to speed up the production of medical protective clothing for the country's fight against the novel coronavirus (COVID-19) outbreak.

A subsidiary company of the China National Nuclear Corporation (CNNC) has started to adopt the irradiation sterilization, a key step to increasing the production efficiency for protective clothing, according to a report by the Science and Technology Daily on Thursday.

With this method, sterilization of over 10,000 medical protective suits were completed within six hours, said Kang Siqing, the company's manager.

The irradiation sterilization mainly uses cobalt-60 and electron beams as radioactive sources.

With a certain dose, the gamma rays or high-energy electron beams generated by electron accelerators can kill the bacteria or pathogens and achieve the purpose of disinfection and sterilization, said Yin Yuji, an expert from China Isotope & Radiation Corporation (CIRC) under the CNNC.

By contrast, traditional sterilization using ethylene oxide consumes a much longer cycle of seven to 14 days, which will delay the delivery of the protective clothing to the hard-hit areas by the epidemic.

On Feb. 8, the State Council issued a temporary document to allow companies to use the irradiation sterilization on medical protective clothing, but special marks need to be put on the package.

The new sterilization method has an equivalent effect with the traditional method and can be completed within one day, according to the document.

The CNNC has nine irradiation devices in several cities, including Beijing and eastern China's city of Suzhou. The device in Suzhou has the capability of sterilizing 100,000 sets of protective clothing a day, Kang said.

Compared to the traditional method, the irradiation sterilization is safer, more environmentally-friendly and effective. No wastewater or chemicals are discharged in the whole sterilization process.

The irradiation sterilization can also be realized without damaging the product packaging, which does not produce secondary microbial contamination.

However, the old sterilization method is of lower cost and the new method requires protective clothing to be radiation resistant.

The companies will first sterilize the clothing samples with different irradiation doses and send them back again to the manufactures to check their water penetration, synthetic blood filtration, microbial indexes and other indicators to set the best irradiation dose, Yin said.

With the industrial upgrading, the irradiation method will play an increasingly important role in the sterilization of medical supplies, said Du Jin, chief engineer of the CIRC.