A special flag for that special constituent

Up, down. Up, down. So go as many as 300 flags a day. Each one has its split second of splendor atop a small flagpole next to the dome of the US Capitol. Weather allowing, you can watch the rather unceremonious flag ceremony every weekday at lunchtime. Old Glory, only its top corner clipped to the pole, speeds along its way, trailing like a streamer in the wind.

If the trip is less than dignified, it nonetheless qualifies each 3-foot by 5 -foot flag as having flown over the Capitol, making it highly suitable for members of Congress to send to constituents.

More and more lawmakers are doing just that. Recent years have seen a flag explosion. In 1978 Congress sent out 35,500 flown-on-the-Capitol flags, and by 1980 the number had almost exactly doubled. This year's totals are expected to go even higher.

''I suppose they have a lot of respect for the flag,'' says Christine Benza, who has supervised the congressional flag office for 21 years. Her three-person staff has been expanded by two temporary workers to help fill the orders.

In her tiny basement room with shelves stacked high with flags, her staff types a decorative certificate for each one. It records when that flag flew - or rather, zoomed - over the Capitol, the name of the recipient, and the name of the senator or representative who placed the order.

Requests come from Scout troops, civic groups, and from constituents who want to give a family member a present of a flag that has flown over the Capitol on some special day, such as a birthday.

Individuals who order the flags through their Congress members pay only the cost of the flag, about $7 (a few cents less if bought through a House member and a few cents more through the Senate, since the two houses contract separately to buy flags). For civic groups, the lawmakers often make the flag a gift.

Congress also pays the estimated $70,000 a year to maintain the flag service, which has been operating since the mid-1930s.

Martin Henry of the Quincy, Mass.-based National Fire Protection Association says kerosene heaters have a better safety record than do wood-burning stoves, although there has been a rise in the number of multiple-fatality fires attributable to portable space heaters in general in each of the past four years.

Roger Mitchell, president of the newly formed National Kerosene Heater Association, agrees that there is a risk of fire or burns if the units are used improperly. But he says the automatic shut-off ''tip switches'' are required by the safety-testing Underwriters Laboratories before it approves the devices and that clear warning labels are attached to the units. In addition, owners' manuals spell out the need for safe operation, Mr. Mitchell says.

''We don't feel that they present any more of a hazard than any other appliance used in the home,'' he says.

Critics are equally troubled by what they say is a risk of dangerous levels of carbon monoxide, especially in air-tight or nearly air-tight buildings, because most of the heaters are not vented to the outside.

The new models generally call for the use of ''1-K'' kerosene (also known as ''water clear'' or ''lighting grade'').

A perceived shortage of ''water clear'' kerosene has forced many heater users to turn to less-pure alternatives - even including gasoline - which give off odors that are easily detected (not to mention carbon monoxide). In such cases, safety officials warn users to open windows for better ventilation.

''We don't know of a single incident of carbon monoxide poisoning or asphyxiation due to kerosene heaters,'' says Mr. Mitchell. He cites a recent independent test by a Delaware laboratory that showed each of three operating heaters produced less carbon monoxide in eight hours than did one burning cigarette.

Mitchell also says kerosene, unlike other liquid fuels, is so safe that it can be shipped through the mail.

But are kerosene heaters cheaper to operate than competing devices?

The Minnesota hardware dealer cited in one Kero-Sun ad claims to have saved $ 450 on a February fuel bill by using the heaters in his store. But in their own advertising some rival distributors tend to promote other features of their products - such as ''engineering excellence,'' ''rapid heating,'' and ''handsome wood-grain cabinet'' - while omitting any reference to the costs of operation.

Indeed, the kerosene units, which in earlier years appealed mainly to lower-income persons as a cheap way of heating their dwellings, now seem to sell mainly as prestige items. Suggested retail prices range from about $150 to more than $300, and fuel can sell for as much as $4 a gallon, plus the cost of the container.

The Washington-based Wood Heating Alliance, stung by a frontal advertising attack on wood stoves on the part of one kerosene-heater distributor, maintains that the cost of 1 million Btus of heat from the liquid-fuel units is about $11. 50, compared with $4.17 for the same amount from mixed hardwoods.

Counters Mitchell: ''The key point is that a kerosene heater isn't used to heat an entire house. It's cheaper to heat one room than it is seven rooms. There's no question that (it) is much more economical to operate than a central heating system is. And it offers flexibility and portability that wood stoves don't. If you leave one room and go into another, you can pick it up and take it with you.''

New Shelter magazine concluded that, providing certain other conditions were met: ''If you are willing to set back the central heating system all season long and take on the tasks associated with maintaining the kerosene heater, you may indeed realize some savings.''

None of the safety organizations contacted by the Monitor advises consumers against buying the heaters. Says Phil Dykstra of the National Safety Council: ''If they meet recognized standards, if the kerosene used is top-grade, and if the heater is kept in top-notch order, then we think they are relatively safe for use in one room or two rooms.''

Adds Martin Henry of the National Fire Protection Association: ''We don't take a position on where they should or should not be used. We simply recognize them as a legitimate space heater.''