Perhaps this was true of products of some bygone era, but modern kero heaters burn extremely cleanly and efficiently. You get some soot and odor when you first start them, but once they're warmed up, you'd never know one was in the room, except for the heat they produce. You can avoid the stop and start fumes by doing so outside, if you wish. Like any other heater with an open flame, they consume oxygen and have the potential to produce carbon monoxide, so they shouldn't be used in a tightly sealed area.

I've got two Kerosun heaters that have been working great for 25 years or so, with only a single wick change each in that time. I also heat my house with two Monitor vented kero furnaces. I had one for 15 years before it required ANY maintenance and that was only a $40 igniter coil. It now heats my basement and I have a newer, smaller, quieter, more programmable unit heating the house. Honestly, I can't recommend these products highly enough.