The doormen, concierges, elevator operators and others who make New York's high-rise apartment living high-class have deserted their posts. Only a strike of Perrier water deliverymen could pose a greater threat to a certain life style.

In the trenches on the first day of the apartment-building workers strike yesterday, the atmosphere was clam, but determined.

Olympic Towers, the Onassis-built luxury building at 51st Street and Fifth Avenue, was down to four people trying to cope with the needs of its inhabitants. Martha Pereira, the executive housekeeper, was in charge of th front desk, juggling telephone calls, deliveries from Bloomingdale's, Lord & Taylor and a fish market and dealing with a newly hired security guard who was having a little trouble adapting to his surroundings.

"If a woman in dungarees and a white shirt comes in, you haven't seen me," the guard said to a surprised Pereira. "She wants alimony," he added.

"I don't even know your name," Pereira replied politely under the circumstances.

The executive housekeeper went back to persuading a hesitant, Spanish-speaking maid to go out ot the sidewalk to collect laundry that normally would arrive at her doorstep.

The fact that people had to send their maids or descend to the lobby themselves to pick up packages seemed to be the worst convenience on the first day at Olympic Towers.

Although 37 people normally would have been on duty, Pereira said the skeleton crew of four was getting along without problems. The elevators were set to automatic. No one had complained about having to push the buttons.

Behind the skeleton crew stood an available reserve corps of volunteers from the apartments. Pereira said no volunteers had been enlisted yet, but they would be needed if the strike lasted.

At the Galleria, an almost equally luxurious building at 57th Street and Park Avenue, volunteers were already on the job.

The woman owner of one of the 253 condominiums was behind the front desk monitoring those entering the building. She declined to give her name, but said she found her duty neither boring nor onerous.

Other volunteers were at work sorting mail, a building spokesman said.

Most life-style threatening of all the scenes, perhaps, was the pile of green plastic trashbags close by the Galleria's front desk. "Each of the owners is asked to take one upstairs," the spokesman, who chose anonymity said. "Then, they take their trash down the back elevators."

"To th basement?"

"No, to the curb," he replied.

No one was rolling bandages, but security was clearly a major concern. Many buildings have hired guards from security firms to replace striking guards and a major effort is being made to keep strangers out of luxury buildings for the duration of the strike.

The Galleria spokesman said that several construction teams remodeling apartments in his building had been denied entry because of the strike conditions.

The last apartment workers' strike, in 1976, lasted 16 days and led apartment dwellers to test the definition of cooperative. In many buildings, residents divided up chores like running the non-automatic elevators, guarding the fornt door and taking out the trash. Heat and air-conditioning systems also have to be maintained.

Not all the apartments affected by the strike are for the very rich, but any New York building with a significant service staff is priced beyond those of modest means. Mayor Edward Koch announced two emergency numbers for apartment dwellers with serious health, heat or hot water problems.

The 25,000 members of the Service Employes Local 32B-32J walked off their jobs at 4 a.m. after negotiations for a new contract broke down. The union is asking about $48-a-week increase over three years and the last management offer is $35. The union is also asking for a provision that would give greater job security to its senior workers.