Why do Ethanol Burners Give off an odour when operating?

by Andrew Grzina

Contrary to claims that Ethanol Burners burn cleanly and without odour, there are times when you will smell odour from your Ethanol Burner.

To understand what is going on, we need to explore a little bit of theory and Chemistry. The author is a Mechanical Engineer, not a Chemist. So if anyone knowledgable (such as Chemist), or someone with experience in using burners would like to add their thoughts please do.

In the blog I wrote about what Ethanol is (READ IT HERE->), I noted that we typically use fuel that has been manufactured in Australia by Manildra.

Manildra has three main Ethanol blends that are suitable for use in Ethanol Burners. They are IMS95, IMS100 and SMS100F4. These are also commonly known as "Methylated Spirits"

The formulations are;

  1. IMS95 (Cheapest): Often bearing the label "95% v/v Ethanol". This formulation uses 95% Ethyl Alcohol, 0.25% Methyl Isobutyl Ketone (MIBK), and the balance is water.
  2. IMS100 (mid-priced): Often bearing the label "100% v/v Ethanol". This formulation uses 99.75% Ethyl Alcohol, 0.25% Methyl Isobutyl Ketone (MIBK).
  3. SMS100F4 (most expensive): Often bearing the label "100% v/v Ethanol". This formulation uses at least 95% - 99.75% Ethyl Alcohol, 0.25% Tertiary Butyl Alcohol, and the balance is water.

IMS95 and IMS100 have essentially the same smell in liquid form. SMS100F4 also has an unpleasant odour in liquid form but can be described has having a slightly sweet note to the odour.

We have used all three variants of fuel in our store, and we are of the opinion that the IMS100 has the least odour during combustion compared with the other two.

Others differ on this point, and claim that SMS100F4 has the least odour. These differences are anecdotal and are probably due to different operating conditions.

In our store, we have 186m2 floor space and we always operate an Ethanol Burner eight hours per day every day, summer or winter, when we are open.

There are times when we will have up to three burners running at the same time.

We find that we can have odour in our store due to several conditions, irrespective of fuel type (eg IMS95, IMS100 or SMS100F4).

Both Ethanol and the denaturing agents used in the formulations above are all products of Carbon, Hydrogen and Oxygen. During combustion, ethanol and its denaturing agent convert to Carbon Dioxide and Steam, both of which are non-toxic and have no odour. There are times however when you will have odour from your burner and I will try and explain some of the possible reasons for this below;

Odour on Start-up:

When you start the burner, you may have some odour from pouring the fuel, from fuel that has been left in the burner prior to start-up, for example overnight, and you can get odour from the first few moments of operation.

This is because you are smelling the Methylated Spirits in an uncombusted form. The vapours have had a chance to escape and can be smelt accordingly. The good news is that at this point the odour if noticeable is very minor, and most people will not smell it. The odour will also dissipated rather quickly.

Odour of Methylated Spirits Whilst Operating:

This explanation is a little more anecdotal and is drawn more from our experiences in our store and conversations with our clients regarding their burners.

At this point I am referring to odour during operation that smells a little bit like a mild form of Methylated Spirits. The authour believes that the primary reasons that odour may exist during combustion is;

  • from running the burner on a setting below minimum, to overcome this, increase the burner setting where possible.
  • ventilation in the room is insufficient. This is a giveaway for the need to open a door or window slightly. If you have a larger size room and this is happening, try turning on a fan, such as from an air conditioner (fan only not heating or cooling), or use a simple fan an place it somewhere in the room but not necessarily near the fireplace/burner. It may be a case of the burner not receiving sufficient oxygen near the flame to burn the fuel, thereby some of the fuel is evaporating rather than combusting.

Combustion Odour whilst Burning:

If you smell an odour that is reminiscent of say a candle burning, or a similar combustion type of odour, then your burner is telling you it is time to clean it.

In our store this occurs about once a month from using the burner six days a week and eight hours each day. This type of odour is easily fixed by cleaning the burner.

To clean the burner, we suggest that you take the burner out of the fireplace to a sink (kitchen or laundry for example). Squirt in a small amount of liquid dish washing liquid and with a sponge clean off the built up carbon on the exposed surfaces of the burner.

Rinse the burner until the water is free from suds and runs out clear.

Allow the burner to dry overnight and return it to the fireplace ready to use.

Contaminated Fuel:

If you have used a fuel container that was once used for something else, then it's possible that the fuel has been contaminated. For example, for us to avoid this occurrence we take back used fuel bottles from our clients and they are reused (after washing) for other purposes. Our supplier only ever uses new bottles for fuel to avoid contamination.

Odour on Shut-Down or when Fuel Runs Out:

If you shut down your burner whilst it still has fuel in the reservoir, then the fuel, being hot, will evaporate and give off some Methylated Spirits Odour.

When the burner runs low on fuel, it gets to a point where there is not enough fuel to support combustion. At this point combustion stops and any remaining vapour has the ability to mix with room air and give some off some Methylated Spirits odour. Some of the newer model Ecosmart Burners have been redesigned to minimise this and produce very little in the way of odour when the fuel has run out.

The best way to limit this type of odour it to close off the burner with the lid, cap or slide provided with the burner.

As an aside, in terms of any residual odour, we don't have any in our store! Odour from Methylated spirits is volatile and evaporates and dissipates quickly leaving no residual odour.