The retail union has contacted Woolworths Bowral employees following the news a staff member tested positive for COVID-19.
Shop, Distributive and Allied Employees Association state secretary Bernie Smith advised workers to take all necessary precautions to ensure their health and safety.
"In affected areas we encourage members to wear masks consistent with current health advice, the masks should be provided by their employer, along with instructions on the proper use of masks and a safe disposal process," he said.
"Masks need to be changed during the shift, about every three hours."
Mr Smith said the union would work closely with its members and companies to ensure "the safest workplaces possible".
The SDA has implemented a 10-point health and safety plan to protect workers from COVID-19 exposure.
Recommendations include contactless payments, the installation of Plexiglass screens at cash registers, social distancing signage and an adequate supply of hand sanitiser, gloves and personal face shields to workers.
Companies should also provide free bags or make customers bring their own, increase security at stores, sanitise workstations and equipment regularly and take a zero tolerance to abuse.
The SDA emailed Woolworths Bowral staff on Wednesday with advice on the current situation.
"The Health Department will work with Woolworths on tracing who had close contact with the employee, who will need to be tested and who will need to isolate," a statement said.
Employees have been asked to follow all directions and health advice once tested for COVID-19.
The SDA said Woolworths Bowral workers must be tested if they have any symptoms or if they are advised to do so by the Health Department or Woolworths based on health advice.