C2H5OH (Alcohol / Benzine) Gas Sensor

melinda_nscc

I am hoping to be able to use the C2H5OH (Alcohol / Benzine) Gas Sensor as a Benzene detector. The datasheets for this product mention that it has a high sensitivity to alcohol, and a small sensitivity to benzene. All of the parameters listed are for alcohol detection, as I assume it's main use would be for a breathalyzer application. I was wondering if there were any minimum and/or maximum limits set for the amount of benzene that this sensor will detect?

Leon

You'll probably have to work it out for yourself and calibration will be a problem. You can buy benzene sensors, of course.

You don't have benzene floating about it, do you? It's nasty stuff.

melinda_nscc

I certainly hope I don't!! I just wanted to make sure that it will detect smaller quantities of the nasty stuff. I realize I will have to calibrate it for my use. Thank you for your reply.

Leon

Many years ago, before it was known to be dangerous, I was told to use it for removing concrete floor sealant that one of my maintenance staff mistakenly applied to some plastic floor tiles. I tried it for myself and must have breathed in a lot of it.

Tracy Allen

You are referring to the Hanwei MQ3 sensor from Parallax (#605-00011), or maybe the digital output module (#27904)?

The first thing is to establish what you mean to "detect smaller quantities of the nasty stuff". The MQ-3 data sheet shows response in the range of 0.1 to 10 mg/l. It is dangerous to extrapolate with these sensors. What are the NIOSH standards for benzene (benzine?) exposure?

Leon

Benzine is petrol, IIRC. Benzene is C6H6.

melinda_nscc

That's not good!! Not growing any extra limbs or anything, are you?

Leon

It was over 40 years ago.

melinda_nscc

Thanks Tracy. I guess I should clarify that I'd like to detect benzene from furnace oil (fuel oil #2) in the air, should there be a leak. That is what I mean by smaller quantities. I'm running with a benzene sensor right now, because it's for a school project and my need is based on being able to quickly order a product, as I need to build my project within 3 weeks. EEK!

erco

Speaking of "good cleaners gone bad", check this article on brake cleaner and phosgene gas: http://www.brewracingframes.com/id75.htm

Tracy Allen

Thanks Leon about the difference between benzine (= mixture of pentane, hexane etc. chain hydrocarbons) and benzene.

From the sensor standpoint, there may be a strong difference between the chain-like structure of the alcohol/benzine and the ring structure of benzene. I thought it might be the OH group on the alcohol, but evidently not. I really wonder how they achieve specificity in these metal oxide (usually tin dioxide) catalytic sensors.

I took a look at the e2v gas sensor offerings. The sensors they recommend for benzene are primarily meant for carbon monoxide+hydrocarbons+VOCs. They are not well characterized though, even for CO. Cheap at $7 each, compared to their NDIR (mine safety, explosive limit) sensors at $264 each.

I see NIOSH and OSHA have 8hr/40hr week exposure limits of between 0.1 and 1 ppm. OSHA: 5ppm max for 15 minutes. NIOSH: acute immediate toxicity at 500ppm.

0.1 mg of benzene in 1 liter of air is about 28ppm, by my calculation.

melinda_nscc

Right...probably a huge difference between the two. I guess I'll have to take a look at some other sensors to see what they will detect...

Leon

Tracy:

I must have been well over those limits when I was using benzene to clean that stuff off the floor tiles. One of my job functions was Safety Officer for that facility!