Acting on a letter from President Reagan that declared the conditions at Blair House a "serious emergency," the Senate Environment and Public Works Committee has approved a $7 million request for renovation and improvements of the 115-room complex used to house foreign dignitaries.

This spring the General Services Administration declared Blair House "potentially dangerous to human safety" and officially closed it in late June. Soon after, a chandelier in the master bedroom came crashing down onto the bed. "Fortunately for us, no one happened to be in the bed at the time," said Public Works Committee Chairman Sen. Robert Stafford (R-Vt.).

The closing came after a gas-valve malfunction leaked gas and nearly caused an explosion. Since then, foreign visitors have been quartered at their embassies or at Washington hotels, a practice Reagan decried in his July 26 letter to Stafford: "This is not only a great expense but it also means that we cannot extend to our visitors the level of security or the hospitality they deserve."

Reagan's letter also called many of the house's main systems "antiquated" and said others, such as fire prevention, "either do not exist or are wholly inadequate."

According to a staff summary by the Public Works Committee, Blair House has grown dilapidated. The elevator pits flooded. The floor in the cooling towers leaked into the pantry. Walls and rugs, "some of them irreplaceable," have suffered water damage.

The GSA's "maximum cost estimate" of $7 million necessary for emergency repair includes $1.26 million for heat, ventilation and air conditioning systems, $665,000 for electrical systems, $300,000 for plaster walls and ceilings, $132,000 for bulletproof "transparent armor" windows and $74,000 for communications. Although the committee passed the request easily in a voice vote, Sen. John Chafee (R-R.I.) later expressed "despondence but acceptance of the high cost of the project."

"It works out to $156 per square foot to repair a building," said Chafee. "It seems high but no one begrudges the need to have an excellent facility to house foreign dignitaries. We didn't quarrel with the figures, we accepted them with resignation. I was afraid if we turned it down, it would just come back to us later on at $176 a foot."

The request now goes to the Senate floor. Reagan said he hoped Blair House would be ready for use again in mid-1984.

Located diagonally across Pennsylvania Avenue from the White House, Blair House has accommodated an array of visiting dignitaries, including Nikita Khrushchev, Queen Elizabeth II, King Saud of Saudi Arabia and Prime Minister Nehru of India. In 1950 Blair House was the scene of an attempt on the life of President Harry Truman.

Francis Preston Blair bought the mansion in 1836 when he came to Washington as part of President Andrew Jackson's "Kitchen Cabinet." The U.S. government bought the house and its furnishings from the Blair family in 1942.