I hope this story scares the hell out of you!

[pdwiley]

Originally Posted by WestVanHan

Various oxygen absorber packs are on the market-in a gallon jar that is full-ish, you put one in there and it'll take the oxygen down to .2 % within 2 hours.
Each package is maybe 1/2 teaspoon of powdered iron oxide.

If it's iron oxide, how is it going to absorb oxygen?

Finely granulated pure iron, I can see working. Then you have iron oxide.

PDW

[WestVanHan]

If they have just iron it would take a while (weeks?) for the reaction to start,and likely never will as there is little moisture in there anyways.

But if the reaction is started-and the packets have moisture-they fire right up and suck up the O2.

[ImaginaryNumber]

Wikipedia | Oxygen absorber

Oxygen absorbers are made in different formulations to match the water activity of the foods they are protecting. Some are designed to be used in dry foods such as nuts and dried grains, others with moister foods such as bread and processed meats. In most formulations the active ingredient is powdered iron or iron salts[1], as well as a material to absorb moisture necessary for the reaction from the atmosphere, such as sodium chloride (table salt) or activated charcoal. The oxygen reacts with the iron to produce iron oxides.

[WestVanHan]

The packs say "contains iron oxide" I should contact the manufacturer,they must have them labelled wrong.

[troy2000]

Originally Posted by WestVanHan

The packs say "contains iron oxide" I should contact the manufacturer,they must have them labelled wrong.

Unless they say, 'contains only iron oxide,' they probably aren't wrong.

[latestarter]

I found this

Q.
What is the oxygen absorber and why is it in the foods?
A. Each can contains a small sealed packet of oxygen absorber, also called a desiccant, which is a drying agent containing iron oxide pellets. It absorbs and holds particles of water and oxygen to itself. The desiccants are non-toxic and should be discarded upon opening the cans. If it is not harmful, why do we print “Do Not Eat” on the packet? Because, it's not food and it tastes terrible!

at this site
http://hmcomposite.com/nutricopiaweb/packaging_faq.html

[hoytedow]

Iron oxide can smother you, or at least, harm you. The Egyptians used it in booby traps.
http://www.thefullwiki.org/Haematite

"Ancient Egyptian booby trap
In 2001, Egyptian government archaeologist Zahi Hawass was the first to enter a previously undisturbed tomb, believed to be that of an ancient regional mayor, in the Bahariya Oasis below the town of Bawiti. Upon entering the burial chamber, Hawass discovered a booby trap consisting of 8 inches of finely powdered hematite dust covering the floor and sarcophagus.[5] When disturbed by a tomb robber, the sharp, metallic dust was intended to become airborne and irritate the skin, eyes and mucous membranes, eventually causing lethal siderosis if exposed for long enough. The archaeological team was forced to retreat and don full body suits and respirators in order to confirm the identity of the mummy. Hawass cites the ancient Egyptians' experience with powdered hematite as a paint pigment as proof that they were aware of its irritating properties.[6]"

http://en.wikipedia.org/wiki/Siderosis

"Similar in pathophysiology to Asbestosis"

[WestVanHan]

I was being sarcastic Troy...and I dislike emoticons

Not sure,but I think I recall reading that rusty seawater (bilges) absorbs O2 even better than just having it all over the steel. Maybe the salt speeds it up and/or forms new compounds that absorb even more O2?
I flunked out of chemistry.

I also read years ago about how felled trees can do the same thing in the holds of ships- they decompose a little yet give of a lot of CO2.

Whenever I'm crawling around in my engine room,I always do a few air turnovers first,and every half hour while I'm in there.

Anyways the point of all this is to plant a seed in everyone's head-maybe sometime in the future they'll come across a rusty (or any tight area) space and think twice.

[pdwiley]

Originally Posted by WestVanHan

I was being sarcastic Troy...and I dislike emoticons

Not sure,but I think I recall reading that rusty seawater (bilges) absorbs O2 even better than just having it all over the steel. Maybe the salt speeds it up and/or forms new compounds that absorb even more O2?
I flunked out of chemistry.

I also read years ago about how felled trees can do the same thing in the holds of ships- they decompose a little yet give of a lot of CO2.

Whenever I'm crawling around in my engine room,I always do a few air turnovers first,and every half hour while I'm in there.

Anyways the point of all this is to plant a seed in everyone's head-maybe sometime in the future they'll come across a rusty (or any tight area) space and think twice.

2Fe + 3O2 -> Fe2O3

Been 40 years since first year university chemistry but IIRC this is a stable compound and can't oxidise further. Think about it. Iron salts in a moist medium, different chemistry.

On confined spaces and their dangers, I agree with you. Our standard practice for working in confined spaces in big ships was, never less than 2 people. One working in the confined space, the other as overwatch higher up with breathing apparatus and a radio to hand. When I did my shipboard firefighting course, we had to train with all this stuff so if we ever had to do it for real, we'd know how.

PDW

[troy2000]

Originally Posted by pdwiley

2Fe + 3O2 -> Fe2O3

Been 40 years since first year university chemistry but IIRC this is a stable compound and can't oxidise further. Think about it. Iron salts in a moist medium, different chemistry.

On confined spaces and their dangers, I agree with you. Our standard practice for working in confined spaces in big ships was, never less than 2 people. One working in the confined space, the other as overwatch higher up with breathing apparatus and a radio to hand. When I did my shipboard firefighting course, we had to train with all this stuff so if we ever had to do it for real, we'd know how.

PDW

I work for a natural gas utility. Over the last few years, our definition of a 'confined space' has expanded to the point that if a space normally has no substantial air circulation and you can reach into it, it's a confined space.

Confined spaces require warning signs, and a protocol for testing the air inside before working in them. Sometimes that seems like overkill... for example, the crankcases of our large compressor units are now classified as confined spaces, even though normally our mechanics stand outside them and at most stick their head and shoulders inside. They have to be tested after the access doors are removed, before any work begins.

After reading this thread, those rules don't seem nearly as silly... better to err on the side of caution.

[erik818]

When iron oxidises (rusts) you first get a red colour rust, FeO. This substance will turn brownish when it oxidises further to Fe2O3. Just speculating, but FeO to Fe2O3 might be a quicker process than Fe to FeO and therefore faster to use for removing oxygen. Fe2O3 will also absorb water and form FeOOH, so an additional effect is that the Fe or FeO powder will also dehumidify the air.
Erik

[Submarine Tom]

And, of course we all know what rapid oxidation is, right?

FIRE!!

[dskira]

In Maine two workers die cleaning a city waste tank.
No need for that, a simple measure instrument will have told them to don't go there.