This is one guys review of the Olympian models and here-say about others. Kind of a long read, but does provide some good info about catalytic heaters...
Catalytic Propane Heaters: Catalytic heaters differ from other propane heaters in that the propane is combined with oxygen to create heat on the surface of a hot platinum catalyst, so that there is no flame. The absence of an open flame, and the relatively low temperature (the catalyst in the Olympian glows a faint, dull, red - visible only in the dark) increases the safety, relative to open flames. The catalytic process also results in a nearly perfect conversion of propane and oxygen into harmless carbon dioxide and water vapor, with no significant carbon monoxide produced.
Advantages of Catalytic Heaters:
Portability: Because of the "clean" burning of the propane, a catalytic heater need not be vented to the outside. It can be installed on or in any wall. When used with an attached 1 lb. tank, or connected to the RV's existing propane piping with a flexible propane hose and quick-connect fittings, it is almost as portable as an electric cube heater.
Note that NFPA 58: Liquified Petroleum Gas Code prohibits the indoor use of propane containers holding more than 2 pounds of propane, except in emergencies. There is work underway to eventually approve a special new design of non-metallic propane tank for certain indoor applications.
Directionality: A substantial amount of heat is radiated straight out from the front of the heater, warming the body it is pointed at. Sitting in front of the heater is almost like sitting in front of an open fireplace - the cozy feeling of the radiant heat allows keeping the rest of the room cooler.
Quiet: In very quiet surroundings, a very faint hiss may be heard. In most conditions, this is inaudible.
No Electricity: Most catalytic heaters use little or no electricity - a major advantage when boondocking in cold weather.
Efficient: The catalytic heater is 100% efficient in converting propane to heat. This is a somewhat misleading statement, since a window must be opened slightly while the heater is in use, to remove water vapor and CO2, and to supply oxygen. Even with the heat loss from the open window, the catalytic heater will use considerably less propane than a conventional propane furnace.
Disadvantages of Catalytic Heaters:
High Cost: A catalytic propane heater costs considerably more than a good quality electric heater. The catalytic element may eventually become contaminated and (for the Olympian brand heaters) must be replaced at the factory - a substantial expense. [Note added 9 April 2010: Our Olympian is now 14 years old; Recently, I dug it out of storage for loan to a friend whose home furnace had failed. It still worked just fine after being stored in its protective vinyl cover for about nine years.]
Installation required: Unless you understand plumbing and are "handy", you will have to hire someone to connect the heater to your existing propane supply. I did it myself - see below. Some smaller models use disposable 1-lb tanks. This avoids the installation problem, but makes them much more expensive to operate. Another option is to use a long extension hose to a 20 lb tank which must (by law) be kept outside the living area.
Large Size (for some models): Compared to an electric cube heater, my Olympian catalytic propane heater is substantially larger and more awkward to store. The Coleman product, on the other hand, is quite compact. The propane hose is stiffer than an electric cord, and can't be plugged in to as many locations in the RV. The small Coleman heater can only be used with one-pound tanks, a cost and convenience issue.
Altitude limitations: The models with oxygen depletion sensors can not be used above 5000 to 7000 feet (depending on brand). The Olympian models without ODS can be used up to 12,000 feet, according to Olympian.
Safety Concerns: Any portable heater requires care and common sense. A portable propane heater requires additional care. There is no tip-over shutoff (at least on our model - some brands do include this), although the legs on the portable model make it quite stable. Although the temperature of the heating element is much lower than that of an open flame (and much lower than many electric heaters), it still could start a fire if in contact with flammable material. The flexible hose and connections on a portable heater need periodic inspection for leaks. The propane should be shut off at the source when the heater is not in use. Forgetting to open a window when the heater is in use is a risk. These heaters are often mounted permanently on or in a wall. This eliminates some (but not all) of the above safety concerns.
Product Recommendations:
I have experience with only one brand - Olympian - and what follows below is directly applicable only to this brand. I have heard second-hand unfavorable comments about a Coleman catalytic propane heater, but have not seen one. Vented catalytic heaters are available, but these are lower efficiency, much more restricted in their installation options (requiring a permanent vent through a sidewall of the RV), and may require electricity for a fan.
I would note that the size and configuration of the catalytic medium is very different between the Coleman and Olympian heaters. The geometry of the Olympian looks to me as though is is inherenently more efficient than the Coleman. Also, the catalyst might be a different material with different conversion efficiency. Olympian says the catalyst is platinum (perhaps partially explaining the high cost of the product). Coleman does not identify their catalyst.
Olympian makes several models of heater suitable for RV use. For comparison, a 1500 watt electric heater puts out 5200 BTU/hr. Counting some loss for the required ventilation, the 6000 BTU/hr propane heater is roughly comparable to a 1500 watt electric heater.
Model Heat Output
(min. - max.) BTU/Hr Notes
Wave-3 1600-3000 manual - no thermostat, no electricity needed. Wall or portable mounting options. Piezoelectric spark ignition
Wave-6 3200-6000
Wave-8 4200-8000
3100 ODS 3000 has oxygen sensor; can not be used above approximately 5000 feet above sea level. Wall or portable mounting. No electricity needed.
6100 ODS 6000
8100 ODS 8000
6100 ET 6000 has automatic thermostat; Wall mount only. requires 12v. electricity - 5 amps while igniting, <0.2 amp thereafter.
8100 ET 8000
The "Wave" models may violate RV building codes in some areas, (California and Canada?) making the "ODS" version the only option available in those areas.
If used in an unventilated space, any propane heater will consume oxygen until there is inadequate oxygen for human breathing. The oxygen sensor in the ET or ODS models senses a low oxygen level and turns off the heater if the level gets too low for safety.
Although an oxygen sensor makes the heater safer, it restricts the heater to use at altitudes below about 5000 to 7000 feet, depending on brand. For many RVers, this is a really major disadvantage, since some of the nicest camping locations are at higher altitudes, and the heater's primary use may be for the cool nights found year-round at high elevation.
Because these heaters use oxygen and emit water vapor and carbon dioxide (not carbon monoxide!), any space in which the heater is used must be ventilated (a window opened slightly), both to add new oxygen and to get rid of the excess moisture. Olympian recommends one square inch of free air opening per 1000 BTU/hr of heat output for "rooms of average airtightness". (This means that for the Wave 6 heater, an RV window 2 feet wide would would be cracked open 1/4 inch.) I have found that our travel trailer is leaky enough to provide sufficient oxygen for two people to breathe while the heater is in use without opening windows. A friend with a large high-end fifth wheel trailer has also found this to be true. We ventilate anyway, largely to keep the moisture level reasonable. But it's comforting to know that if we forgot to open a window before going to bed, it wouldn't kill us.
This comment should be understood in the context of our own tolerance for reduced oxygen levels. We have camped at altitudes of 10,000 feet and hiked as high as 14,000 feet without problem. Individuals with impaired heart/lung function, or those who suffer from altitude sickness at much lower elevations, will want to be much more careful about ventilation.
For our 35' travel trailer, we chose the 5800 BTU/hr manual model (similar to the current Wave-6 model) and fitted it with legs and a 10' flexible hose for portable use. We also purchased a fitted vinyl cover, to preserve the life of the platinum catalyst by keeping out dust and dirt while the heater is not in use. As of December, 2011, the Wave-6 is available on the Internet for about $250, plus around $13 for the legs, about $19 for the cover, and about $35 to $80 for flexible hose and copper fittings to tap into the existing propane piping. RV Solar Electric offers both a fixed and portable installation kit, each containing everything needed for a typical installation.
My installation was rather simple. My furnace is under the sofa in the living area, in the middle of our trailer. I unscrewed the propane line from the furnace, screwed a "T" fitting into the furnace, screwed the propane line back into one leg of the "T", and attached a shutoff valve and the flexible line to the other leg of the "T". When not in use, the catalytic heater, still attached to the hose, slides under the sofa, in a vacant space adjacent to the furnace. The 10' of hose is sufficient to allow placing the heater most of the way down the hallway, pointing into the rear bedroom, or in the kitchen pointing at the dinette seating, or pointing at any of the seating positions in the living area. (This is an easy do-it-yourself project, but only if you understand basic plumbing procedures and materials and understand how to test for propane leaks).
Our 35' travel trailer (without slide-outs) is fairly average as to air infiltration and insulation quality - some are significantly worse, and some are significantly better. Under typical conditions, our 5800 BTU/hr heater's high setting will maintain the entire trailer at 25 to 30 degrees above the outside temperature. The specific region toward which the heater is pointing will be about five degrees warmer, and a person at which the heater is pointed will feel even warmer because they are absorbing the radiantly beamed heat. With this heater, we have boondocked comfortably in night-time temperatures down to about 27 degrees. We generally travel so as to stay in areas where the night-time temperature is rarely below 50, and under these conditions, the lowest setting can be too warm. For many people, the smaller 2800 BTU/hr heater would be a better choice. In very large or poorly insulated rigs, or for colder climates, the big 7600 BTU/hr model may be desirable.