How many times have you read that something was bad for you or dangerous only to later find out that it wasn’t as bad or as dangerous after all?  Such is the case with the kerosene heater.  Daily reminders on every danger imaginable have created a population afraid of almost everything.  Behind this fearmongering is usually a root agenda for more government regulation or a financial interest on the part of someone trying to steer you to a “safer” alternative from which they will coincidentally benefit. 

This guide focuses on wick-type kerosene heaters.  I wrote this to inject some common sense into the discussion on kerosene heater use.  I have used them safely for years.  I do not work for or have a financial interest in any entity associated with the HVAC industry.

There are two main styles of wick-type kerosene heaters: Radiant and Convection.  Radiant heaters are characterized by their rectangular shape and their heat is projected in one direction, from the front of the unit.   Convection heaters are distinguished by their circular tower design and their heat is distributed omni-directionally.  Radiant heaters are the better choice for heating smaller areas (350-400 sq. ft); convection units are more appropriate for larger areas (900-1,000 sq ft).  Most radiant units are rated at 9,000 to 10,600 BTU’s.  Convection heaters are typically rated at 20,000 to 23,000 BTU’s.  Early kerosene heaters used an all-cotton wick. During the middle of the 20th century, manufacturers began to switch to a cotton/fiberglass wick, which lasts longer and permits dry-burning (a wick cleaning technique discussed below).  Virtually all kerosene heaters made since the 1970's use a cotton/fiberglass wick.  

Kerosene heaters have been around for over a century.  Today’s models burn cleaner and have safety features not even dreamed about years ago.  Although some still criticize kerosene heaters as “dangerous”, no alternative is without some kind of risk.  Consider the hazards of being without electricity for an extended period including exposure to the cold or risking an accident by venturing out onto ice or snow-covered roads to get to a public shelter for warmth and then dealing with the health consequences (such as influenza and bacterial infections) common to any crowded and confined space.  What if the power grid, which affects electricity and natural gas, takes a hit?  What about the potential dangers and property damage from frozen pipes when you are without heat in sub-freezing conditions? 

Let’s look at some data, as reported by the publication “HOME FIRES INVOLVING HEATING EQUIPMENT” - National Fire Protection Association, dated November 2007:

• From 1980 to 2005, fires attributed to stationary and portable space heaters declined by 66% (and by 76% from the peak in 1983), despite Heating Degree Days (heating demand) being comparatively constant over the same period.
  Source: Home Fires Involving Heating Equipment (November 2007), National Fire Protection Association, pp. 8, 31
• The Annual Average Percentage of home fires traced to space heaters by fuel type during the period 2002-2005 is as follows:
  o 64% electric-powered
  o 19% gas-fueled
  o 16% liquid-fueled (kerosene, diesel fuel, number 1 or 2 fuel oil)
  o 1% solid-fueled (coal, wood).
  Note that fires involving oil-filled heaters that are, in fact, electric-powered are miscoded as portable kerosene heaters by a 2-to-1 margin (Source: Home Fires Involving Heating Equipment (November 2007), National Fire Protection Association, p. 33).  Therefore, the percentage of fires actually attributed to liquid-fuled (kerosene) heaters is lower than the 16% stated above. 
• Cooking equipment, not space heaters, has been the leading cause of home fires since 1990 (Source: Home Fires Involving Heating Equipment (November 2007), National Fire Protection Association, p. i).  This lends some perspective on the relative risks of space heating. 
   
  While it is true that central heating systems have a smaller fire risk than space heaters, the leading causes of space heater fires are due to user-error.  Think about it: The most interaction users have with a central system is setting the thermostat.  Space heaters, on the other hand, require more user involvement.  Eliminate the user-error and space heater safety is on a par with central systems.  Below are some guidelines.  The first two items alone account for one-half of all space heater fires. 
  1. Keep the heater at least 3 feet away from combustible materials.  Draperies are of particular concern since wind drafts can cause them to move.  Placing any heat source, (electric, gas, wood burning, or kerosene) too close to combustibles is the number one cause of space heater fires. Source: Home Fires Involving Heating Equipment (November 2007), National Fire Protection Association, p. 41.
  2. Do not leave the unit unattended, especially if kids or pets are around – the same precaution you should take for an oven or barbecue grill.  A watched pot never boils!  This is the second leading cause of space heater fires.  Source: Home Fires Involving Heating Equipment (November 2007), National Fire Protection Association, p. 41
  3. Never use gasoline in a kerosene heater – in any amount. 
  4. When refueling a kerosene heater, turn it off, let it cool, and refuel it outside.  Do not overfill the unit.
  5. Read the owner’s manual and familiarize yourself with the heater’s operation.  Owner’s manuals are considered legal documents and much thought goes into writing them.
  6. Keep the heater clean and well-maintained.
  7. What about carbon monoxide (CO)?  A CO detector is always a good idea.  Any fuel burning appliance, including wood as well as vented and central gas furnaces, can emit carbon monoxide if not working properly or is oversized for the area being heated.  I have operated my kerosene heaters near a carbon monoxide detector with a digital readout.  The detector never budges from zero – even after running for hours.  However, when I start the car, even with the garage door wide open and the detector on an opposite wall, I get readings almost immediately from the car exhaust.  This tells me two things: (1) The CO detector works and, (2) My heaters are well maintained and properly sized for the area being heated. 
  8. Bigger is not necessarily better when choosing a kerosene heater.  Kerosene heaters operate in a relatively narrow output range, meaning you cannot adjust the heater up or down more than about 5-10% from its rated output.  Therefore, you should not purchase a kerosene heater with the mindset, “Well, I’ll get the larger unit so I have the higher output when I need it and dial it down when I don’t”.   An oversized unit will force the user into frequent cycles of shutting the unit off when the room gets hot, only to restart it when the room gets cold.  A properly sized unit may be left on for an extended period of time while keeping the room at a constant comfortable temperature. 
  9. Wick-type kerosene heaters have an inherent safety characteristic that you never hear about: The burner cannot become flooded with fuel even if the heater should extinguish unexpectedly (which would take an extraordinarily strong gust of wind).  This is because the wick draws up kerosene until it becomes saturated, then its capillary action ceases.  It is like dipping one-half of a rag into a sink full of water and suspending the top half of the rag above the sink.  The rag could not drain the sink and flood the area because when it becomes soaked, it cannot absorb more water.  This is a natural behavior of the wick and it does not rely on any complex mechanical or electronic safeguards.

All kerosene heaters require basic maintenance:
1. If the unit takes longer than normal to warm up, or you notice a strong odor when the unit is running at normal operating temperatures, the wick may need to be dry-burned.  Dry-burning means letting the heater operate until it runs out of fuel and extinguishes itself.  This cleans the wick and restores its capillary efficiency.  To do this, remove the side fuel tank from the unit (radiant models) or siphon most of the fuel out of the tank on convection models.  Then, light the heater and let it run until it extinguishes.  This process takes about an hour.  Because dry-burning can generate odors when the process nears completion, it is best done outside or in an area sheltered from wind such as a garage or shed with a door or window open.  After dry-burning, refill or top off the fuel tank.  Wait at least a half-hour before lighting the heater.  Since dry-burning dries the wick, it needs time to saturate with kerosene before lighting.  This waiting period should be observed whenever you fill a “dry” heater, such as after dry-burning or the initial use of the heater of the heating season.  NOTE:  If you have an older kerosene heater with an all-cotton wick (such as a Perfection heater), do not dry-burn the unit. 
2. At the end of the heating season, remove all fuel and dry-burn the unit.  Although the tank may be empty after dry-burning, trace amounts of fuel may remain in the sump.  This fuel must be removed from the unit before storing, even if it means disassembling the unit (which is relatively easy to do).  Removing all traces of fuel before any extended period of storage eliminates the risk of fuel going stale.  It also prevents water vapor from condensing in the sump and causing rust which could then lead to fuel leaks.  After removing all fuel, click the shut-off button on the heater to make sure the wick is completely lowered.  This also reduces tension on the spring that raises and lowers the wick.  Finally, remove the igniter batteries from the unit.
3. Keep the box that came with the unit as it can be used to store the heater.
4. If you are really particular, apply a coat of automotive wax to the metal exterior of the unit, including the safety grill.  Then wipe thoroughly before storing.  This will ward off rust and keep the unit looking new.

Kerosene heaters have been safely used by millions of people for over a century.  Although most people in the U.S. use kerosene heaters for supplemental or backup heat, they are still used today as the primary heating source throughout much of the world by diverse societies ranging from the Amish to high-tech Japan.  Kerosene heaters are safe to use with only the usual precautions required for anything that generates heat.  Consumers should have the right to assess the risks/benefits of kerosene heater use and evaluate it against alternative risks without infringement by paternalistic third parties.