(a) A county, a public health district, or the department may require certification under Subchapter D, Chapter 438, for each food handler who is employed by a food service establishment in which food is prepared on-site for sale to the public and which holds a permit issued by the county, the public health district, or the department. This section applies without regard to whether the food service establishment is at a fixed location or is a mobile food unit.
(b) The requirements of certification under this section may not be more stringent than the requirements of Subchapter D, Chapter 438.

(c) A county, a public health district, or the department may not require an establishment that handles only prepackaged food and does not prepare or package food to employ certified food handlers under this section.
(d) A county, a public health district, or the department may exempt a food service establishment from the requirement that the county, public health district, or department has imposed under Subsection (a) if the county, the public health district, or the department determines that the application of Subsection (a) to that establishment is not necessary to protect public health and safety.
(e) A county, a public health district, or the department may require a food service establishment to:
(1) post a sign in a place conspicuous to employees, in a form adopted by the executive commissioner, describing a food service employee’s responsibilities to report certain health conditions to the permit holder under rules adopted by the executive commissioner; or
(2) require that each food service employee sign a written agreement in a form adopted by the executive commissioner to report those health conditions.