The investigation team of CCTV's "Is it true" program bought three ordinary mobile phone cases made of plastic, silicone and leather from stalls and shopping malls respectively, and sent them to indoor air testing Room of Tsinghua University Building Environment Testing Center for testing. Through analysis, it is found that the mobile phone case will release toxic substance formaldehyde at the average temperature of normal use, and the leather mobile phone case has the highest release amount of 0.25mg/m3, which is more than twice the national indoor air standard. The investigation also found that the plastic mobile phone case bought in the stall had the highest benzene emission, which was 0.0494 mg/m3, while the leather mobile phone case bought in the shopping mall had the lowest benzene emission, which was 0.0 19 1 mg/m3, but both of them did not exceed the national indoor air standard of 0.1kloc-0/mg/m3.