Boston — A sure way to start an argument among some Americans these days is to bring up the subject of products imported from Japan. This is particularly true of kerosene-fueled space heaters.
But it isn't their ''made in Japan'' labels that make these devices controversial. Instead, it is their appropriateness for use in the home.
Critics tend to come mainly from the ranks of the firefighting and fire-prevention community or to be makers of rival types of space heaters. But the liquid-fuel units have their defenders, too, including some in nationally known safety agencies.
Kerosene heaters unquestionably are popular. Last year alone, by some estimates, 2 million of them were sold in this country, and as many as 5 million may be in use now. Kero-Sun, the industry leader, will sell ''in excess of 1 million'' over the 1981-82 heating season, asserts company spokesman Neil Morse.
Kero-Sun has been running two-page ads featuring a Minnesota hardware dealer and a North Dakota priest who testify to their satisfaction with the company's heaters in their store and parochial school, respectively. Almost at the bottom of the second page - in small print - however, the ads recommend that potential buyers ''check local codes for permitted uses'' and note that some states prohibit operation of the heaters in buildings used for human habitation.
In fact, California, Massachusetts, and - technically - New Hampshire and Ohio ban the sale of such heaters or their use in the home. (The New Hampshire law has been temporarily set aside by a state court on an appeal by Kero-Sun; the state attorney general is weighing his next move. And the Ohio law will be in effect only until March 17, when a new measure will allow the sale and use of some kerosene units.) Wisconsin has banned their use in multifamily dwellings, although they are legal in one- and two-family houses.
Many cities and towns also have banned the heaters, although enforcement is generally considered all but impossible.
If anything, enforcement may have been undercut by the refusal of the US Consumer Product Safety Commission in 1980 to ban the sale of kerosene heaters nationally on safety grounds. Commission spokesman James Hoebel says, however, that although the request for the ban (by the city of Newark, N.J.) was denied, ''We are concerned about kerosene heaters. We're alert to the emergence of any problem. However, we haven't seen it yet.''
On the other side of the ledger, at least five states (Maryland, Delaware, New York, Connecticut, and Rhode Island) either have reversed or relaxed their bans on kerosene heaters this year.
Even critics concede that the new generations of the Japanese-made heaters, which began penetrating the US market in the mid-1970s, are safer, more efficient, and more aesthetic than those of a decade or so earlier. But the same critics aren't ready to give up yet.
Their arguments tend to fall into four major categories:
* That there is a risk of burns or fire from positioning a working heater too near combustible materials, from careless operation, or by the accidental tipping over of some units, even though most of them feature automatic shut-offs designed for just such contingencies.
* That there is a risk of unsafe buildups of carbon monoxide because of the burning of low grades of kerosene or substitute fuels.
* That many people, for the sake of convenience, store fuel indoors in unvented containers.
* That kerosene heaters can be as expensive to operate as other methods of heating - if not more so.
Says Capt. Donald Perrault of the Hartford, Conn., Fire Department, which has asked for a ban on their sale or use in the city: ''There's no problem with the heaters themselves; it's the handling. They're supposed to be filled outside, but you know and I know that most people . . . are going to fill them indoors, and some are even going to fill them while they're still running.''