In the face of parents' doubts about the excessive formaldehyde in the classroom decorated for two months in a primary school, the principal of the primary school responded: I have been to all the classrooms one by one and didn't smell any peculiar smell, so the formaldehyde doesn't exceed the standard.
 Even for rooms without peculiar smell after decoration, formaldehyde may exceed the standard within a few months after decoration can best refute the certification of the primary school principal.