Spending for the Homeland Security Department expires Friday at midnight if Congress doesn’t act before then. With lawmakers at loggerheads over immigration provisions in the agency’s annual funding bill, it’s not certain how the Capitol Hill stalemate will end.

Here are five things to know about what happens in a shutdown of the Homeland Security Department:

YOU MIGHT NOT EVEN BE ABLE TO TELL IT’S HAPPENING

Democrats and the Obama administration are raising concerns about shutting down the department at a time of worldwide security threats, but such rhetoric is at times overblown. In reality, a shutdown would only be a partial shutdown.

Of the department’s 230,000 employees, some 200,000 of them would continue to report to work even if the department is not funded, because they are deemed essential for the protection of human life and property. That includes front-line workers at agencies including Customs and Border Patrol, the Secret Service and the Transportation Security Administration. Airport security checkpoints would remain staffed, the Secret Service would continue to protect the president and other dignitaries, the Coast Guard would stay on patrol, and immigration agents would still be on the job.

However, those workers would go without a paycheck until the shutdown is resolved. Department leaders emphasize this creates major morale problems for their workforce, especially since many of the workers are younger border patrol or airport checkpoint agents who do not have a lot of savings.

SOME ACTIVITIES WOULD TAKE A HIT

The approximately 30,000 workers who would get furloughed during a shutdown include administrative staff, front office workers, and people who train new hires at the Federal Law Enforcement Training Centers.

Hiring would stop, as would research and development work on projects such as cargo screening technologies. People responsible for operating and maintaining the E-Verify system that allows businesses to check the immigration status of new hires would be furloughed.

In addition, people responsible for writing and administering emergency preparedness and response grants at the Federal Emergency Management Agency would be told not to report to work, leading to pleas to Congress from governors, mayors, fire chiefs and others to keep funding going.

“There’s real impacts to our ability to support the recovery from Sandy, Katrina, the Colorado floods, you name it, because our ability to continue paying and the rebuilding of those disasters will be delayed and postponed, and it will not be made up,” FEMA Administrator Craig Fugate said Monday.

IMMIGRATION ACTIONS WOULD CONTINUE

The dispute over the Homeland Security funding bill involves GOP language overturning President Barack Obama’s executive actions that extended deportation stays and work permits to millions of immigrants in the United States illegally.

Most of those policies are on hold anyway after a federal judge blocked them last week, a ruling the Obama administration is appealing.

But if the Obama administration is successful in getting the judge’s stay lifted, the immigration programs would continue even in the event of a shutdown. That’s because U.S. Citizenship and Immigration Services, which is responsible for administering them, is funded by fees, and fee-funded programs continue unaffected in a government shutdown. Unlike most other workers who report during a shutdown, those funded by fees even get paid.

WHY ARE WE DOING THIS AGAIN?

After the last government shutdown — 16 days in the fall of 2013 in a failed GOP attempt to gut Obama’s health law — Republican leaders vowed to avoid a repeat.

But Obama’s executive moves on immigration shortly after Democrats were routed in the November midterm elections incensed conservatives, setting up the current impasse.

While Congress passed a full-year spending bill for most government agencies in December, lawmakers kept the Homeland Security Department on a short leash. The idea was to use the agency’s annual spending bill as a vehicle to oppose Obama over immigration once the new Congress was seated with Republicans in control of the Senate and holding greater majorities in the House.

But when the new Congress convened in January, Republicans quickly found that they didn’t have much more leverage than before, thanks to Obama’s veto pen and Senate rules giving significant rights to minority Democrats.

The House in January passed a $39.7 billion bill funding the Homeland Security Department through the current budget year Sept. 30, while also overturning Obama’s immigration policies.

Senate Democrats have now united on four filibusters blocking action on the House-passed bill.

CONGRESS HAS OPTIONS — JUST NOT OPTIONS LAWMAKERS LIKE

Democrats are demanding a “clean” DHS bill stripped of the contested language on immigration. A few Republicans in the House and Senate have backed that option, too, saying the fight over immigration should play out in the courts, especially now that a federal judge has sided with them.

But many House Republicans say they can’t support a clean bill. Senate Majority Leader Mitch McConnell, R-Ky., is seeking a way out by calling for a separate Senate vote on some of the immigration provisions from the House bill, but it’s not clear if that gambit will succeed.

That leaves lawmakers with one other option aside from a shutdown: a short-term extension of current funding levels.

A number of conservative Republicans say they would oppose such a measure, and agency leaders warn it would leave them short of the resources they need. But it could be where a Congress that can’t agree on anything better ends up.

(AP)