The salt used for halotherapy is pure grade sodium chloride (also known as medical-grade or pharmaceutical-grade salt) which is the highest purity salt, often used in medical applications. It is 99.99% NaCl and contains no insoluble ingredients and is free from all other contaminants. This type of salt is placed in a device called a halogenerator which grinds the sodium chloride into micron-sized particles to form a dry salt aerosol that is inhaled in a salt chamber environment. Digesting salt and dry salt inhalation are very distinct. Pure grade sodium chloride is the only salt approved by the Salt Therapy Association for use in halogenerators for several reasons.