The impact and cost of a shutdown really depend on how long it lasts. The full scope of the shutdown would not be felt until Monday when hundreds of thousands of non-essential federal employees are furloughed.

Secretary of Defense Jim Mattis said on Friday that a government shutdown would impact military operations, including some training and maintenance.

Federal workers considered “essential to national security and public safety” would work through a shutdown. That includes federal law enforcement officials, TSA screeners, air traffic controllers, federal doctors, firefighters and border patrol agents.

“All of these people will be working for nothing, which is simply not fair,” said White House budget director Mick Mulvaney on Friday.

The employees would be paid for their work after a budget resolution is passed.

However, most federal agencies would be closed, such as the Department of Education and the IRS, except for essential functions.

The EPA would remain open through January 26, according to a memo sent from the administration to employees on Friday.

Around half of Health and Human services employees would be furloughed. That means the CDC would operate on “minimal support,” despite a deadly and widespread flu season.

Here’s how other HHS departments would be affected

What’s open, what’s closed:

The post office remains open and mail will be delivered.

Federal courts would remain open.

The Interior Department has indicated it will work to keep the parks open; other public lands will try to allow limited access, according to a spokeswoman.

Museums such as The Smithsonian and the National Zoo would close on Monday, but remain open for the weekend.

Benefits

Government benefits such as Social Security, Medicare and Medicaid, should not be impacted by a shutdown.

What about CHIP funding?

The Washington State Health Authority says the state has enough CHIP (Children’s Health Insurance Program) funding to keep the program operating until “sometime in February,” according to a spokeswoman.

Related: Gov't shutdown deadline nears; Senate sets one last vote

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