It was very hot and very smoggy in the car inspection station in Northeast Washington when Curtis Jackson's 1968 Pontiac Ventura finally moved up through the long line and into the middle inspection lane.

This was Jackson's second attempt in a week to get a valid inspection sticker, and this time, he said, he thought he had it made.

He stepped down on the gas pedal as instructed.

A cloud of gray smoke billowed out of the exhaust pipe.

An inspector was hit in the face with the smoke as he bent over a nearby car. "Hey!" he yelled, glowering at Jackson, who looked straight ahead. Another inspector ushered Jackson and his offending car outside the building and told him to get his muffler fixed before trying again.

Jackson, 47, who works as a Metro bus driver, was unhappy but philosophical about this latest defeat at the hands of the inspectors and he was not without ideas for resolving the entire matter. "I don't see any smoke," he said as little puffs of gray floated from his car's tailpipe. "But I ain't going to worry about it . . . . I'll just sell it to somebody and let them fix it."

Each weekday from 6 in the morning to 2 in the afternoon, the 44-year-old red-brick building at 1827 W. Virginia Ave. NE becomes one of the city's great social levelers, where Porsches and Plymouths, rusted wrecks and polished chrome come together in the annual ritual of passing the District's car inspection.

Rich and poor, young and old, the patient and the impatient, wait in line for 10 minutes to an hour to present their cars and receive the inspectors' verdict. The station is one of two responsible for inspecting all cars registered in the District. The 16-member, all-male crew at the station works its way through an average of 600 vehicles a day, inspecting an average of one vehicle a minute.

The car owners, often with children in tow, tend to remain silent, their arms folded firmly across their chests.

Or they shift nervously from foot to foot and lean out into the lane to see just what the inspector is looking at.

The end result of the process is a bright red, diamond-shaped rejection sticker or a blue-green, rectangular inspection sticker good for one year.

Harry Proctor, supervisor for the Northeast station, said that about a third of all the vehicles are rejected for safety violations and about four a month are deemed so dangerous that they are given a large bright yellow and red condemned sticker.

In one busy noontime hour recently, two Mercedes, one Metro bus, two school buses, one Fleetwood Cadillac limousine, two District police scooters, one Park Service police car, one truck carrying a hydrocrane, a city-owned trash truck, a spiffy Fiat convertible with the top down, and numerous taxicabs and family cars passed by the inspectors.

The Metro bus, one of the police scooters, and an assortment of taxis and ordinary cars got the rejection sticker.

Among the fortunate last Friday was Nancy Jones, who brought in her 1981 VW Rabbit convertible. Wearing a straw hat and a stylishly short, white and red dress, she greeted inspector George Howard warmly as he slid into the driver's seat.

"He's a gem and a gentleman," said Jones. "I've been through before and he is always very nice."

Leslie James, who has been driving school buses for the Sidwell Friends School for 21 years, got his 1974 Ford school bus through inspection with ease. "We take good care of the buses. If I'm driving it, I want it to be safe," he said.

"There are no tricks to getting through inspection," James added. "They don't take no hand-me-downs bribes in there. They won't go for that."

And the proud owner of the smoky green, Fiat Spider convertible exuded confidence in his car's driving condition. "I'm not going to have any problems," said Derek Medlock, 28, a telephone installer. "I drive it every day and it's in fine shape." Ten minutes later, Medlock, wearing Ferrari sunglasses, gave the thumbs-up sign as he exited the inspection station with the blue-green sticker.

Life in the inspection lane is not without hazards, said Howard, 55, a big, friendly man who always has advice for the motorists with rejected cars.

A nine-year veteran of the inspection division, who worked as a mechanic for a rental car agency before he became an inspector, Howard said he likes his job.

"The only thing wrong is the smog you have to work in. You go home every day and you're all drug out and you fall asleep. On bad days, you keep a headache all day right at the top of your head."

Drivers who put their cars into reverse--instead of park--also can be a problem, said Davis Middleton, 29, who has been an inspector for three years. "You go to look at the taillights and here comes this car right at you.

"Then there are the drivers who put the car in drive, and it takes off down the lane. We yell, 'loose car,'" he said.

Last week Howard and Leslie Harris were working as "sticker men," a position that rotates on a weekly basis.

Based on the emissions test he conducts, and the assessment of the other two inspectors on his team, the "sticker man" decides the fate of the car before him, attaching a rejection sticker or an inspection sticker to the windshield.

They are the ones who explain to the owner why a vehicle has been rejected.

"These are economic hard times," Howard said.

"We will give them a little extra time for nondangerous violations to fix their cars if they have already tried to fix them."

"This is a safety program, not a rejection program. This is a ghetto neighborhood and we get the older cars here. If a person is pressed for money and the car is rejected, they feel rejected."

As his work day ended, Harris wished the owner of a rejected taxicab a good day, just as he had the other drivers all day.

"No matter what they call me, names I wasn't given at birth," he said, "I still say 'Okay, have a nice day.' "