Magnetometers have been used for years at all visitor and staff entrances to the Capitol and many other federal buildings.

But lawmakers have been allowed to go around those security screenings provided they were wearing their congressional pin.

That changed Tuesday, ahead of two consequential votes beginning in the evening that address the potential removal from office of President Donald Trump.

The decision was made by the House sergeant-at-arms.

"To provide a safe and secure environment in which to conduct legislative business, effective immediately, all persons, including members, are required undergo security screening when entering the House chamber," Acting Sergeant-at-Arms Timothy Blodgett said in a statement.

"Failure to complete screening or the carrying of prohibited items could result in denial of access to the chamber."

Lawmakers are allowed to carry guns on Capitol Hill, but "firearms are restricted to a member's Office," Blodgett said.

Workers were seen installing one of the metal detectors in front of one of the chamber's doors, while two others were already in place at other entrances. A fourth was awaiting installation.

The move comes six days after pro-Trump rioters laid siege to the Capitol, disrupting Congress as it voted to certify the election win of President-elect Joe Biden.

Five people died after the violence engulfed the seat of US democracy.

The protocol change also comes after a first-term Colorado Republican, Lauren Boebert, said she would bring her Glock to Congress and that government should not be allowed to dictate how she can protect herself or her family.

"I will carry my firearm -- in DC, and in Congress," she said in a video posted on her Twitter account on January 3, the day she was sworn in as a member of the House.

The video shows her loading her gun, putting in her hip holster and walking the streets near the Capitol.

Guns have been banned from the House floor since 1967.

Boebert is co-chair of the newly formed Second Amendment Caucus, aimed at supporting the protection of the constitutionally-enshrined right to bear arms.