Breathalyser test process A video posted on PM Lee's social media pages captured each stage of the two-minute long breathalyser test process on July 26. First, he was briefed on how to use the handheld breathalyser by a worker in full protective gear. He then blew into the breathalyser for around 10 seconds, before closing the tube. The tube was then disinfected: And placed into a reader for analysis: The result was then displayed on a computer screen: In a candid moment of the video, PM Lee could be heard confirming his result, asking: "So, negative?" The staff then assured him that he was indeed Covid-19 negative.