However, other references recommend a minimum 20-minute flushing period if the nature of the contaminant is not known. The flushing or rinsing time can be modified if the identity and properties of the chemical are known. If irritation persists, repeat the flushing procedure. Non-penetrating corrosives are chemicals which react with human tissue to form a protective layer which limits the extent of damage.
Most acids are non-penetrating corrosives.
Penetrating corrosives, such as most alkalies, hydrofluoric acid and phenol, enter the skin or eyes deeply. It is important to get medical attention as soon as possible after first aid has been given. OSH Answers has more information on emergency eyewash and shower equipment . In the past, oxygen was commonly recommended as a first aid procedure for almost any chemical exposure. It is now recognized that administering oxygen can be harmful if carried out improperly or in the wrong circumstances.