Welcome Guest! The IOSH forums are a free resource to both members and non-members. Login or register to use them

Postings made by forum users are personal opinions. IOSH is not responsible for the content or accuracy of any of the information contained in forum postings. Please carefully consider any advice you receive.

Notification

Icon
Error

Options
Go to last post Go to first unread
bluewater  
#1 Posted : 21 August 2015 14:03:18(UTC)
Rank: Forum user
bluewater

How would you go about measuring the LEL for Benzene in a confined space. Is it still measured in parts per million. I read somewhere that the LEL for Benzene is 800ppm. However I have little experience in measurement or contact with this substance. any help will be greatly appreciated.
Kate  
#2 Posted : 21 August 2015 14:21:05(UTC)
Rank: Super forum user
Kate

You don't measure the LEL (lower explosive limit), you look it up (for example on a safety data sheet - it will be under physical properties). What you might measure is the actual concentration of benzene to compare it with the LEL. You need a gadget for that and a trained person to operate it (without entering the confined space to do so).
bluewater  
#3 Posted : 21 August 2015 14:54:39(UTC)
Rank: Forum user
bluewater

Kate wrote:
You don't measure the LEL (lower explosive limit), you look it up (for example on a safety data sheet - it will be under physical properties). What you might measure is the actual concentration of benzene to compare it with the LEL. You need a gadget for that and a trained person to operate it (without entering the confined space to do so).
Thanks Kate, I could not get my head around the 800ppm as being an LEL...wish I could remember where I had read that, I'm sure it was an American safety page on the web.
HSE_Steve  
#4 Posted : 21 August 2015 15:10:00(UTC)
Rank: Forum user
HSE_Steve

Hi Bluewater, quite a specialist field this, be careful! The 8hr TWA Workplace Exposure Level for Benzene is 1ppm. Be aware that the limits in the UK and US are often very different. Steve
Ron Hunter  
#5 Posted : 21 August 2015 16:19:48(UTC)
Rank: Super forum user
Ron Hunter

The 'gadget' Kate refers to being an explosimeter I believe.
bluewater  
#6 Posted : 21 August 2015 16:41:18(UTC)
Rank: Forum user
bluewater

Thanks Guy's
gotogmca  
#7 Posted : 24 August 2015 15:01:42(UTC)
Rank: Forum user
gotogmca

Blue, The LEL for benzene is 1.3%, which equates to approx. 13,000ppm. Modern flammable gas detection equipment is usually to set to alarm at a percentage of the LEL e.g. 10%. However, as already stated you do have to consider the WEL (workplace exposure limit) and this is significantly less than the LEL. So whilst the area might be safe because the LEL is not exceeded, workforce exposure would be well exceeded. Hope this helps.
PIKEMAN  
#8 Posted : 24 August 2015 15:40:09(UTC)
Rank: Super forum user
PIKEMAN

I believe that the WEL for Benzene is due to its "narcotic" properties; as it is a Carcinogen then you should be looking for going "ALARP" as regards exposure. When I used to manage entries like this we would vent and purge so that there were negligible levels of flammables and Benzene - and even then, we would use Breathing Apparatus for the entry. I would advise; use extreme caution and get competent, if not expert, advice. As soon as I saw "Benzene" and "Confined Space" in the same sentence, I took a deep breath.......................!!!
johnmurray  
#9 Posted : 24 August 2015 15:54:56(UTC)
Rank: Super forum user
johnmurray

bluewater  
#10 Posted : 24 August 2015 18:02:00(UTC)
Rank: Forum user
bluewater

Guy's, A colleague sent me these today, which may or may nor be of use to you all in the future. http://www.rapidtables.c...umber/PPM_to_Percent.htm / http://www.rapidtables.c...umber/Percent_to_PPM.htm 1. Benzene LEL – 1.3% / UEL – 7.9% 2. Converted from PPM AT 70ppm is 0.007% 3. LEL 0f 1.3% = 13000ppm
bluewater  
#11 Posted : 24 August 2015 18:03:04(UTC)
Rank: Forum user
bluewater

JohnMurray wrote:
https://www.gov.uk/government/uploads/system/uploads/attachment_data/file/316487/Benzene_guidance.pdf
Thank you John.
Jesper Scott  
#12 Posted : 24 February 2018 13:04:12(UTC)
Rank: New forum user
Jesper Scott

Originally Posted by: johnmurray Go to Quoted Post
https://www.gov.uk/government/uploads/system/uploads/attachment_data/file/316487/Benzene_guidance.pdf

Thank you for the pdf. Exactly this is what i was looking for. 

I also found couple of coverter links that might be helpful .

https://www.calculatorology.com/ppm-to-percent-converter/

https://www.calculatorology.com/percent-to-ppm-converter/

Hsquared14  
#13 Posted : 26 February 2018 09:36:15(UTC)
Rank: Super forum user
Hsquared14

I'm not sure why you would want to measure anything relating to a Lower Explosive Limit, its usually in the % range of contamination whereas exposure is generally in the parts per million range.  If you need to monitor flammable gasses / vapours in air say for confined space entry then you need a  flammable gas/vapour  monitor like this https://www.crowcon.com/...cts/portables.html  - other brands are of course available and you need to select one that does what you want it to do. 

Users browsing this topic
You cannot post new topics in this forum.
You cannot reply to topics in this forum.
You cannot delete your posts in this forum.
You cannot edit your posts in this forum.
You cannot create polls in this forum.
You cannot vote in polls in this forum.