Walmart and Sam’s Club customers will soon be required to put on a mask or face covering before shopping in stores. 

The big-box retailer announced the new policy Wednesday and said it will take effect July 20. It said the majority of its approximately 5,000 stores and clubs  — about 65% — are in areas where there’s already some kind of government requirement for face coverings.

With the new policy, Walmart joins a growing list of retailers that require masks inside of stores. Best Buy started requiring face coverings in its stores Wednesday. Costco and Apple already had the requirement.

The Centers for Disease Control and other federal agencies have recommended face coverings as a way to prevent the spread of the co..., especially when physical distancing isn’t possible. Face coverings can also limit the spread by people who do not have symptoms, yet can spread the virus to other people.

The requirement has taken on new urgency for public health officials and companies, as Covid-19 cases and hospitalizations rise across the U.S.

Walmart U.S. Chief Operating Officer Dacona Smith and Sam’s Club Chief Operating Officer Lance de la Rosa said in a post on the company’s website, the new requirement will keep customers and employees safe and “help bring consistency across stores and clubs” across its national footprint.

“While we’re certainly not the first business to require face coverings, we know this is a simple step everyone can take for their safety and the safety of others in our facilities,” they said in the post.

Many retailers, including Walmart, have dealt with a patchwork approach of state and local rules about face coverings. Without a national mandate, their employees have often had to police mask wearing policies — whether their own policy or a local government mandate.

In some cases, enforcing the requirements has led to confrontations between employees and customers and viral social media videos.

Best Buy originally encouraged, but did not require face coverings. The company’s CEO Corie Barry said in May that the company has provided training on how to de-escalate situations, as employees have served customers who are “scared, frustrated and occasionally hostile.”

“It can range from customers being frustrated that they can’t just walk into a store and get what they need to customers potentially not wanting to wear masks,” she said on a phone call with reporters.

In the website post, Smith and de la Rosa said the company will post signs and train employees. All stores will have a single entrance. 

At Walmart stores, the company has created a new employee role to enforce the requirement. Each store will have a health ambassador who will get special training and will be stationed near the door. That person will remind customers about the mask requirement when they walk inside. 

Health ambassadors will be identified with a black polo shirt, they said. He or she “will work with those who show up at a store without a face covering to find a solution that works for everyone,” according to the post.

At Sam’s Club locations, an employee will also stand by the door and remind customers about the requirement. Complimentary masks will be provided or be available for purchase.