Should You Use A Kerosene Heater In A Greenhouse? [You Should!]


Isn’t it scary to use gas like kerosene in such an enclosed space? Fumes and fire might be your main concerns. The good news? Yes, you can, but with some measures

Kerosene heaters are widely used in greenhouses as fuel-efficient, convenient, effective, and safe heating sources during winter. However, proper safety precautions such as ventilation systems, cleaning, maintenance, with some common sense measures are required to prevent fire accidents and toxic fumes.

To be honest, it’s not that scary when you realize that kerosene heaters are tried-and-tested machines used in domestic and greenhouse spaces! All you have to do is follow proper safety precautions.

Kerosene Heater in a Greenhouse?

Kerosene heaters are a common heating solution for greenhouses. They provide a cheap, reliable, effective, and mostly safe source of heating for greenhouses during cold seasons and for cold climates.

There are two most common types of greenhouse heaters: 1) electrical heaters and 2) gas heaters. Kerosene falls under the gas heater type.

Gas heaters are traditional heating methods which have the distinct advantage of being able to easily provide high temperatures while operable without a power source. However, its distinct disadvantage is that it runs on gas which produces condensation and toxic fumes that can cause serious problems if not properly controlled.

The Advantages of Kerosene Heaters

Kerosene heaters have some key advantages which make them an attractive option for heating.

  1. They are cheap and widely available.
  2. Surprisingly effective at heating up a space.
  3. Fuel-efficient, capable of lasting up to 16-24 hours
  4. Newer models are less odorous.
  5. Does not require a power source apart from batteries to work.

The Disadvantages of Kerosene Heaters

However, kerosene heaters also have an equal number of disadvantages due to their gas operation.

  1. Kerosene heaters produce toxic fumes which can be deadly to human and plant life at high concentrations.
  2. Refilling can be a hassle and a hazard.
  3. Spare fuel canisters should always be present.
  4. Condensation is produced.
Kerosene Heater Greenhouse – Infographic

Are Kerosene Heaters Safe Indoors?

Kerosene heaters are safe to use indoors but still require some caution to use in indoor environments, especially in greenhouses.

While kerosene heaters provide a cheap, efficient, and effective source of heating during colder climates and seasons, there are still inherent hazards in using a machine that consumes fuel and produces heat.

1 – Oxygen Deprivation

Kerosene heaters require oxygen to combust and continually burn. However, a lack of oxygen due to a lack of proper ventilation can cause incomplete combustion of the fuel which reduces the amount of heat produced and creates carbon monoxide.

Carbon monoxide is a colorless, odorless gas that can pose a serious threat if breathed over a period of time in higher than normal amounts. It is poisonous to humans and also harmful to plants. Plant leaves curl, yellow, and show other abnormalities.

This production of carbon monoxide in an enclosed space is the most important consideration because it presents the most immediate yet unforeseen hazard of kerosene heaters.

2 – Pollutants

Kerosene heaters also emit other chemicals such as carbon dioxide, nitrogen dioxide, sulphur dioxide. These chemicals may have negative effects on human or plant health at high concentrations.

Carbon Dioxide can be utilized by plants in the process of photosynthesis when they absorb the gas through their stomata. According to NASA, an increase in carbon dioxide for plants can increase growth, yield, and reduce water loss that occurs through transpiration

Nitrogen Dioxide, at high concentrations, may have negative or positive effects on plant growth and development. However, studies regarding its effects have no conclusive findings hence it is safer to keep concentrations moderate rather than extreme.

Sulphur Dioxide, at high concentrations, can inhibit the photosynthesis process. The stomata’s opening is influenced by the presence of sulfur dioxide which results in excess water loss via transpiration.

3 – Fires, Explosions, and Burns

As with any device which uses gas and outputs heat, Kerosene heaters may cause fires, explosions, and cause bodily harm when handled improperly.

Fires can occur when the heater is too close to combustible material such as wood, dry organic matter, or plant leaves. It is important that they are placed from a safe distance from combustible material. Kerosene fuel may leak or be leaked during the refueling process which may cause fires.

Explosions can occur when refilling is done while the heater is in use. It is also important to use the correct type of fuel instructed by the manufacturer.

Finally, burns (1st degree or worse) can occur when the heater is touched while it’s in operation or from the residual heat immediately after it is turned off.

Safety Precautions in Using Kerosene Heaters in Greenhouses

To prevent the inherent disadvantages of kerosene heaters, proper safety precautions should be installed and practiced.

1 – Ventilation

Proper ventilation is not only a necessary precaution to prevent the buildup of toxic fumes and condensation from kerosene heaters but also crucial for a successful greenhouse. Proper ventilation promotes temperature control, air flow, pollination, and pest management.

A ventilation system could either be passive or powered. Passive ventilation systems merely involve ridge vents which allow cold air to displace the warm air inside. Powered ventilation systems (PVS) use fans and vents to regulate and circulate the air inside the greenhouse. Passive ventilation may be quiet but are less effective and cost-efficient than powered ventilation systems.

A ventilation system can prevent the buildup of toxic fumes which are harmful to plant and human health, namely: carbon monoxide, sulfur dioxide, and nitrogen dioxide. Releasing these toxic fumes outside makes the inside of the greenhouse safer for plants and humans.

Proper ventilation also has the added benefit of allowing outdoor CO2 to be absorbed by plants. Gas exchange is crucial in the photosynthetic process.

There are also instances where a greenhouse can be too warm even in cool weather and climates. A greenhouse that is too warm is detrimental to plants, especially those with weak heat tolerance. Allowing excess heat to escape might seem counterintuitive but the objective of a greenhouse is to maintain ideal growing temperatures and just raise the temperature.

Fresh air distributed evenly is conducive to plant growth and development. It allows for cross-pollination by way of animals, insects, or wind currents. The introduction of fresh air also reduces overly humid conditions which cause water accumulation. Accumulation of water via droplets or pools is favored by pests.

2 – Using 1-K Kerosene or the Recommended Kerosene

1-K grade kerosene is recommended however only the proper fuel or grade of kerosene should be pumped into a kerosene heater to prevent explosions or other hazards. Always read the manufacturer’s instructions on what grade of kerosene to be used.

1-K or One-K grade kerosene is the highest grade of kerosene and its purest form. It has a maximum sulfur content of only 0.04% making it safer for indoor use. Because of its refined nature, it does not require a flue to filter out combustion byproducts.

2-K or Two-K grade kerosene is a lower grade of kerosene and less refined than 1-K. It has a maximum sulfur content of up to 0.30% and requires a flue to filter out the byproducts of combustion. Because of this, these are not optimized for indoor use.

3 – Refilling A Kerosene Heater

Always follow the manufacturer’s instructions on how to refill a kerosene heater and never refill the heater while it is in operation. Always refill the kerosene heater outdoors where there are no combustible materials to make sure that fire does not spread in case of an accident.

Always make sure to check the fuel gauge and be sure to refill before the tank is completely empty. A siphon pump should be used when applicable.

Kerosene canisters should be placed in a cool place, preferably in a garage or basement where there is no heating source. When stored properly, its shelf life can last for 2-5 years.

Never mix kerosene with other gas fuels. Finally, kerosene should not be placed in gasoline canisters or vice versa.

4 – Cleaning and Maintenance

A clean kerosene heater prevents safety hazards. The wick should be checked every week and cleaned as per manufacturer specification. Regular cleaning and preventive maintenance prevent gunk, dirt, and other debris from hindering the smooth operation of the heater.

The wick should be cleaned from debris and ash buildup because this prevents it from lighting or continually burning. When there is something wrong with the kerosene

Kerosene heaters should be cleaned with water, towels, brushes, and non-combustible cleaning materials. Non-combustible cleaning materials are a necessity because leftover cleaning residue will not react to the heat.

Gas spillage during the refilling process should be wiped away immediately to make sure it will not catch fire due to sparks or heat.

How To Clean A Kerosene Heater

Finally, it’s also a good idea to perform some preventive maintenance every year. Dust, debris, carbon deposits and the occasional insect nests can accumulate inside a kerosene heater which will prevent a heater from turning on, turning off, or maintaining a smooth operation.

5 – Moving A Kerosene Heater

A kerosene heater in operation should not be moved while it is turned on. It should be turned off and given time to cool before moving.

Moving a kerosene heater while it’s in operation is a fire hazard. You must avoid doing so especially in a crowded greenhouse with tall or wide plants that might accidentally touch it.

Extinguish the flame and give it 5-10 minutes to cool before moving to the desired location. Make sure that the desired location is not close to combustible materials or other sources of heat.

6 – Buying A Modern Kerosene Heater

Modern kerosene heaters have better safety features, are more fuel-efficient, and are less odorous.

Older kerosene heaters have the problem of being odorous which may cause discomfort and annoyance to users. This odor problem is usually experienced when turning on or turning off a heater.

Aren’t Greenhouses Already Warm Enough?

Greenhouses might not be warm enough during colder seasons in very continental weather. Greenhouses during the winter might require additional heating to prevent the plants inside from frost, especially sensitive ones like parsley.

Greenhouses in cold climates are vulnerable to indoor temperatures falling too low from being ideal. Plants exposed to extreme cold are subject to chilling and freezing injury.

Freezing damage occurs when plants are exposed to freezing temperatures i.e. lower than 32 F (0 C). Here we have a full guide to herb temperature tolerance. The water inside the plant freezes into ice crystals which cut cell membranes. It can cause plant tissue to brown or blacken, leaves and stem to curl, and finally wilt.

Chilling injury occurs when plants are exposed to non-freezing temperatures i.e. ~32-55 F (~0-10 C). The effects of chilling depend on the tolerance of the plant to the cold, with tropical or subtropical plants being the most affected. Chilling can cause the plant to exhibit discoloration, curling, and even wilting.

The Ideal Greenhouse Temperature

The ideal greenhouse temperature is 80-85 F (26.67-29.44 C). However there are two main factors that significantly affect heat retention and transfer: 1) the R-Value and K-Value, and 2) Air Flow.

R-Value and K-Value

Heat loss in greenhouses is measured by “R-value” (Heat Flow Resistance). The higher the value, the less heat is lost. The K-value (Thermal Conductivity) is the overall heat transfer coefficient of materials. The lower the value, the less thermally conductive material is.

These two values are essential in computing the BTUs needed, along with the greenhouse volume and heat differential. Heaters are measured in BTUs (British Thermal Units) to better convey the power of a heater.

This online calculator can help you compute the minimum BTU required for your greenhouse.

Air Flow

A greenhouse cannot be airtight. Air flowing from the outside to the inside and vice versa is necessary. Ventilation is required to induce proper air flow.

However, the air flow must be controlled. Leaks and cracks cause the warm air indoors to escape and cold air to enter. This lowers the indoor temperature and causes chill or freezing damages to plants and crops.

Air flow can be beneficial to reduce the indoor temperature, preventing it from being too hot or too humid inside. Air flow can also facilitate the exchange of gases such as carbon dioxide and oxygen.

Which Type of Kerosene Heater Is Better?

There are two general types of kerosene heaters: 1) convection, and 2) radiant.

  1. Convection Heaters – these are better suited for larger greenhouses. The heat transfer occurs through the surrounding air rather than directly heating the objects around it.
  2. Radiant Heaters – these are better suited for smaller greenhouses. They are more energy efficient and warms the surrounding objects rather than the air surrounding it.

For most cases, a convection heater is a superior option since it delivers heat by propelling the heat through the air. This avoids burning the plants too close unlike in radiant heaters.

The type of kerosene heater you will use depends on how large your greenhouse is. Needless to say, the larger the greenhouse, the more powerful the heater required.

Kerosene Heater Recommendations

For small and medium greenhouses, we recommend the one below.

For larger greenhouses that require ~30,000 BTUs, it’s a good idea to consult your local gardening stores, greenhouse stores, or indoor heating professionals to better explore your options.

Are Kerosene Heaters Cheaper Than Electric Heaters?

Kerosene heaters are often cheaper than electric heaters as the former are more fuel-efficient at creating heat. It is estimated that kerosene heaters are 90-92% efficient.

Though kerosene heaters are more expensive to buy (investment cost) than electric heaters, they make up for it by being less expensive to operate (running costs). Kerosene heaters can reduce heating costs from $100-$600 during the winter seasons.

Finally, depending on which part of the world you are in, kerosene is a much more inexpensive fuel source than electricity. In conjunction with the kerosene heater’s fuel efficiency, it reduces the operational cost during the colder seasons.

Takeaways

  1. Kerosene heaters are tried and true machines that provide adequate heating for greenhouses while being economical and fuel efficient.
  2. Kerosene heaters come with distinct disadvantages owing to their gas-based operation. As with anything that uses combustible liquid, it’s important to implement and practice proper safety precautions.
  3. Kerosene heaters are initially more expensive but cheaper to run long term due to the price of kerosene compared to electricity.

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Andrea

A young Italian guy with a passion for growing edible herbs. After moving to the UK 6 years ago in a tiny flat, it was impossible to grow herbs outside. So I start my journey in growing indoor and so I decided to share my knowledge.

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