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Explosive limits


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My distillery is being audited by our Australian work-safe government agency.

A report I was given says I must not allow the alcohol vapour to be greater than 5% of the LEL (lower explosive limit)

I have seen on this forum that in USA that is 25% of LEL. Is that correct?


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I would need more information.

5%, where?  In your still or around your facility? 5% in your still is nothing, but in your facility it's a big deal.  LEL of ethanol is closer to 3.3% as well.  We (Texas, USA) are required to have flame arrestors on our still, receiving tank, and heads/tails tank.  They are all supposed to stay closed when alcohol of any content is present, and we need to constantly be pulling from our distillation room to ensure we don't have flammable vapors.  We are now trying to get an alcohol meter on our floor that would only kick on the fans to remove air from the room when that limit is reached.  Otherwise our A/C is fighting against the removal of the air in the room.

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3 hours ago, Bakery87 said:

I would need more information.

...... 5% in your still is nothing, but in your facility it's a big deal.  LEL of ethanol is closer to 3.3% as well. ......................

Our state Workplace Regulations says 5% of the LEL.  That is 5% of 3.3% = 0.165%

I would assume without further tedious reading that that means anywhere workers are going to be.

Our National Regulations says the same 5% but that is only in cool stores (where there is almost no ventilation)

I am quite sure I will need to get a alcohol meter to do tests, possibly one with a logger so I can record what happens over a period of time.

Any suggestions on buying one that won't cost too much?, I have a very small operation.


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Hi Pete,

We use an RKI PS2 as do many other distillers in the US.  We're happy with it.  If it hits its limit it turns on an exhaust fan that is about 18 inches above the floor.  We test it once a year with butane that I am told has similar properties to ethanol vapor to see if the alarm goes off and if the fan comes on.  We also have it sounding an alarm.  The cost of the device was less than $500 USD.  I think the test kit was extra>

It seems that your spec is dramatically stricter than ours.  You are correct, we are 25% of 3.3%.

You and @Silk City Distillershave been around this forum for a long time.  Perhaps you should PM Silk to get his take on this.

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  • 3 weeks later...

Thanks for the above advice.

I have purchased a personal monitor RK GP-03 for AU$400. It has been set for initial alarm at 5% LEL then a second level 10% LEL.

I sat it in the lowest point of my bond store this morning and it read ZERO. There is a small amount of natural ventilation in there.

For the rest of the day it sat on the floor next to the still while it was doing a stripping run. It read zero all day except when we poured a small amount of the output onto the floor to mimic a spill and it indicated 1% of LEL for a minute or so.

Very encouraging results.

My still is direct flame heated, burning waste fryer oil. The burner has a reasonably large fan to assist correct air mixture so it continually removes volatiles from the still area and into the fire box.

I did lower the sensor into the air space in a drum of 45% whisky. The alarms sounded at 5% and 10% as I gently lowered it. When it was almost on the surface of the whisky the readout was 88% LEL.

Very interesting observations.

I will probably end up purchasing one for each of my employees to wear. They are designed to clip onto clothing.

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