The purpose of this study was to explore the relationship between the transmission of respiratory diseases and the correct wearing of masks, as well as the factors affecting the correct wearing of masks. The research is beneficial to the prevention of respiratory diseases and moves the barrier of prevention and control forward. It is of great significance to COVID-19 's practical prevention and control.

1. Overall design：This study uses the methods of cross-sectional survey and chance sampling.
2. Sign the Informed Consent Form.
3. Investigation on the basic situation of personnel: The gender, age and education level of the subjects were analyzed as the factors influencing whether the mask was worn correctly or not.
4. Investigation on the types of wearing masks： 1) The types of masks worn by the subjects were recorded as the basis of stratified statistics.

2) Mask suitability testing：

1. Visual inspection whether the mask is close to the face with obvious gaps.
2. Breathing test whether it can blow the cotton wool under the eyes when the subject taking a deep breath.
3. Spray test The FT-30 qualitative fitness test system of 3M company was used to test the suitability and correctness of wearing mask.

In the spray test, all subjects underwent a sensitivity test to prove their ability to smell the bitterness of the reagent, and then were randomly divided into a hood group and a direct spray group.

In order to objectively reflect the overall situation of the subjects, it is necessary to cover many ages and educational levels of men and women.

Each subject participated in the study for about 5-6 minutes, and the total duration of this study was about 3 months.

Inclusion Criteria:

1. Healthy people with autonomous behavior ability and language expression ability who are older than or equal to 7 years old, Persons under the age of 18 need to obtain the consent of their legal guardians；
2. The subjects and / or their legal guardians have the ability to understand the contents of the study and to participate in all the research processes with the subjects；
3. People who volunteered to take part in the study；
4. There was no respiratory infection in nearly one month.

Exclusion Criteria:

1. People with a history of allergies, including those who are allergic to pollen, dust mites, etc；
2. People with any history of drug allergy；
3. People who have participated in the experiment are not allowed to participate in this study for the second time;
4. Pregnant women；
5. The healer after COVID-19 's infection；
6. After questioning, it was found that the subjects were the factors that affected the study, such as dysosmia, or those who had decreased olfactory ability due to disease, or facial paralysis, which affected the judgment of the test；
7. Those who are participating in clinical trials of other drugs / devices；
8. Subjects with poor compliance or unwilling to cooperate with the operation as required；
9. The researchers believe that any other situation that may affect the evaluation of the study.

Those who are 7 years old or above, have the ability of autonomous behavior and language expression, are willing to take the test.