heat packs and oxygen

[kbekker]

The heat packs that are put in with tarantula shipments consume oxygen. I realize the oxygen demands of most shipments are minimal and that the containers are rarely sealed, but...

Has anyone ever had a shipment in winter run out of oxygen? Very large heat pack, very small container, mysteriously dead tarantulas?

 

[gvfarns]

That's a really good observation! Usually we just don't worry about oxygen for the T's. Maybe that's the cause of some of these mysterious deaths we see in winter shipping.

 

[UrbanJungles]

The amount of o2 necessary to cause the oxidation reaction which releases heat is a tiny amount at best. Unless you have a hermetically sealed & airtight box, o2 will find its way in.

 

[equuskat]

The amount of o2 necessary to cause the oxidation reaction which releases heat is a tiny amount at best. Unless you have a hermetically sealed & airtight box, o2 will find its way in.

I agree with this. The chances that a T dies of asphyxiation in a box because of a heat pack consuming oxygen is unlikely at least, and I doubt it's possible.

I'd say that winter deaths have the same causes as summer deaths: mishandling, molts in transit, and exposure to extremely high or low temps.

 

[kbekker]

Probably true, but adding oxygen accelerates the reaction, indicating that the level of atmospheric oxygen may regulate the heat packs. The oxygen consumed is very measurable, often done at science fairs. And if you put one in a "smaller" sealed container it will run out of oxygen and stop heating.

Do you have a reference to how much oxygen they actually consume?

 

[KJE]

I think what we have to remember here is that t's don't require much oxygen to survive. I have received t's in containers with no air holes and they were fine after 2 days in shipping.

 

[kbekker]

I realize the oxygen demands of most shipments are minimal

Thats what I meant by the above statement, but they do need oxygen

 

[equuskat]

Since there is a constant flow of oxygen (as air) into the box, the breathing air won't run out. Presumably, the heat pack will "suck" oxygen in to continue the reaction (obviously on a small scale). There will always be more air. Shipping boxes are not airtight containers, so this discussion is essentially moot. While it is a good science fair project, it really doesn't have relevance in shipping tarantulas.

 

[gvfarns]

Since there is a constant flow of oxygen (as air) into the box, the breathing air won't run out. Presumably, the heat pack will "suck" oxygen in to continue the reaction (obviously on a small scale). There will always be more air. Shipping boxes are not airtight containers, so this discussion is essentially moot. While it is a good science fair project, it really doesn't have relevance in shipping tarantulas.

Sorry to be contrary but this doesn't seem obvious to me. If you tape all the edges of a carboard box with packing tape it can be pretty hard for air to cross over.

Regarding heat packs sucking air in, I don't know what the actual chemical reaction is, but I know of no reason to think it's converting gasses to solids. More likely it's some slowed down version of burning, so it sucks oxygen and produces CO2. Would this create negative air pressure? Actually the carbon or whatever is burning will go from a solid to a gaseous state, possibly forcing some air out if anything.

I'm not saying it is a problem, but I see a lot of people being quite dismissive of what seems to me to be a real possibility.

 

[Steven Valys]

Regarding heat packs sucking air in, I don't know what the actual chemical reaction is, but I know of no reason to think it's converting gasses to solids.

"Some hand warmers contain cellulose, iron, water, activated carbon, vermiculite and salt and produce heat from the exothermic oxidisation of iron when exposed to air.

A second type generate heat through exothermic crystallisation of supercooled molten materials (usually sodium acetate) and are reusable. These can be recharged by boiling the warmers and allowing them to cool. Heating of the pads is triggered by snapping a small metal device buried in the pad which generates shock waves to initiate crystallisation.

A third type uses lighter fluid (lighter fuel) or LPG which is reacted with a platinum catalyst to release heat by oxidation reactions. These can be used on many occasions by simply refuelling." Yahoo! search results

 

[kbekker]

"Some hand warmers contain cellulose, iron, water, activated carbon, vermiculite and salt and produce heat from the exothermic oxidisation of iron when exposed to air.

This is the type that form the vast majority used in animal shipments.

Maybe its not a problem, but without actually knowing how much oxygen is needed for the reaction, I would be hesitant to say its not important.

 

[barabootom]

I recently shipped some large slings in a completely sealed styro, tight fitted box with a 40 hour warmer. (No air in, no air out) I shipped across the whole country by express and after 24 hours everything arrived in excellent condition. The heat packs that are meant for shipping animals consume very little oxygen and stop heating if the air runs out. I'll admit I was a little concerned, but I experienced no problem whatsoever.

 

[equuskat]

You can go nuts taping the edges, but cardboard is quite air-permeable. You will never run out of air in a cardboard box, even if the edges are triple-taped. If you cover the ENTIRE BOX in tape (with no cardboard exposed), however, that's making a very closed environment. However, most people don't cover an entire box in tape. Cardboard is PAPER. It's extremely breatheable.

The heat pack does not physically suck in oxygen, but it WILL continue to use the air that flows into the box, and yes, there is exchange through the cardboard. Likewise, CO2 can escape the box.

I still say that the risk is extremely minimal.

 

[DrAce]

...The heat pack does not physically suck in oxygen, but it WILL continue to use the air that flows into the box, and yes, there is exchange through the cardboard. Likewise, CO2 can escape the box.

...

Yes, it does suck in oxygen. Selectively, no less. If the box really was sealed, the atmospheric pressure would drop. Quickly.

It'll even do it on an appreciable scale - 20 g of iron in a hand-warmer will consume somewhere around 1.5 Litres of pure oxygen (certainly in the litre range) - this is calculated using moles (iron is going to iron III oxide), then using room temperature to calulate a volume using the ideal gas law (PV=nRT). I don't know if there are 20g of iron in a handwarmer, but it seems like a reasonable sorta volume of iron filings for a handwarmer sized thing.

Fact is, this could, in reality, be a problem...

But spiders use practically no oxygen, particularly if they're cool - which is variable because of the hand warmer - and also as mentioned, the boxes are not air-tight. Also, the handwarmer will not produce any gasses as a result of this - no CO2 will be coming out.

The slight risk is that the handwarmer does this reaction quite quickly - it'll be all over and done with after a few hours.

 

[Protectyaaaneck]

chemistry is fun.

 

[DrAce]

I think so. That's why I teach it. I don't mean for that answer to be definitive, but an estimate, made really quickly. It'd be right to an order, for certain.

 

[Protectyaaaneck]

I think so. That's why I teach it. I don't mean for that answer to be definitive, but an estimate, made really quickly. It'd be right to an order, for certain.

hah, no I was being serious, it was one of my favorite subjects in both high school and college.

 

[jasen&crystal]

I think what we have to remember here is that t's don't require much oxygen to survive. I have received t's in containers with no air holes and they were fine after 2 days in shipping.

I received an adult T in sealed container after 3 day's shipping and she was fine. I wander how much a T uses when they cant move around much? I always put in air holes but maybe its not nessasarey.

 

[DrAce]

I received an adult T in sealed container after 3 day's shipping and she was fine. I wander how much a T uses when they cant move around much? I always put in air holes but maybe its not nessasarey.

Probably not. The problem/concern is if they are sitting around for more than 3 days for some reason. It's not inconceivable for them to be there a week.

An air-hole isn't going to cause harm.

 

[Tony]

Since there is a constant flow of oxygen (as air) into the box, the breathing air won't run out. Presumably, the heat pack will "suck" oxygen in to continue the reaction (obviously on a small scale). There will always be more air. Shipping boxes are not airtight containers, so this discussion is essentially moot. While it is a good science fair project, it really doesn't have relevance in shipping tarantulas.

Yes, it does suck in oxygen. Selectively, no less. If the box really was sealed, the atmospheric pressure would drop. Quickly.

It'll even do it on an appreciable scale - 20 g of iron in a hand-warmer will consume somewhere around 1.5 Litres of pure oxygen (certainly in the litre range) - this is calculated using moles (iron is going to iron III oxide), then using room temperature to calulate a volume using the ideal gas law (PV=nRT). I don't know if there are 20g of iron in a handwarmer, but it seems like a reasonable sorta volume of iron filings for a handwarmer sized thing.

Fact is, this could, in reality, be a problem...

But spiders use practically no oxygen, particularly if they're cool - which is variable because of the hand warmer - and also as mentioned, the boxes are not air-tight. Also, the handwarmer will not produce any gasses as a result of this - no CO2 will be coming out.

The slight risk is that the handwarmer does this reaction quite quickly - it'll be all over and done with after a few hours.

Overall how much difference in Volume will there be once the heat pack is 'consumed'? That answer will help determine if any 'sucking' is going to take place.... If it consumes oxygen and replaces it with some other gas, well we will have convection inside the box but very little 'draw' from the outside.
I have gotten boxes (well sealed) with COLD 40 hour packs. Left out these packs warm up again to an extent, so ....Was there too little oxygen in the box?

Ultimately if your concerned for the spider, simply ship in its own 'diving bell' - a sealed deli cup or vial with it's own private O2 supply...
Tony