2000 C5 Explosion Under Hood

[northernlights]

Well....I'm not a chemist either! And, after reviewing my post, it seems that I do not have enough education to know when to properly use a 's...like after Fords!

The EPA book is interesting. As implied, one of the advantages of CFC's were their chemical stability. I really don't have the knowledge to intelligently comment about ODP or chemical stability of R22, but it almost looks like there may have been a double (or more) extrapolation based on observations. For example, for R12 the logic appears to be, chlorine attacks ozone, R12 has chlorine and is chemically stable so it will hang around, so R12 has a high ODP. R22 also has chlorine, but it is less chemically stable than R12, so at least it will go away, so R22 has some ODP but less than R12. But, it seems strange that the chemically stable compound (R12) will somehow provide more reactivity (from the Cl- ion) with greater ODP than the less chemically stable R22.

Note the EPA paper states on page 10:

HFCs do not contain any chlorine and therefore do not have an ODP.

which implies that Cl is believed to be the culprit. Is that the case? Who really knows.

Purely from an engineering perspective, my main issue with the GWP, and one reason for my comment, is the number of significant figures reported, i.e. 3 in the case of 1430. In practice very few things are that accurate, so it is misleading to the public to imply more accuracy than is realistically possible. That alone makes me skeptical of the source data, because a good scientist/engineer would not exaggerate the accuracy of one's findings. (footnote: I think that apostrophe is correct!) And quite frankly, understanding what the numbers mean can often put things into perspective as far as what is relevant and what isn't. In my opinion, driving a 10 mpg vehicle is far worse than a little R134a venting. But, so some degree this is where we get into the sticky subject of politics and opinion vs science.

[instarx]

As far as R-134A goes you, as a car owner (As of this posting) can vent it without fear of going to EPA jail. A professional, working for hire, cannot legally vent it to the atmosphere though. R-134A is an HFC refrigerant which has no Chlorine and thus it poses no harm to the Ozone layer. If for no other reason than the cost of the refrigerant it is never advisable to vent it though.

...Lee

Lee, technically you are correct, R134a has very little effect on the ozone layer. But there is more to the story of R134a than ozone. R134a is moderate to strong greenhouse gas 1,400 times more potent than CO2. It has a GWP (Global Warming Potential) index of 1,430 which is only a bit less than HCFC-22, one of the worst of the old chlorinated fluorocarbons (GWP 1,800). Although it does not significantly deplete the ozone layer, it does contribute significantly to global warming through other greenhouse mechanisms. So the inference that most would make after reading your post -- that it is OK to release R134a directly to the atmosphere -- would be wrong.

Dude, you might want to park your car.

Assuming R134a has 1430x the GWP of CO2, means that if the OP manages to vent one pound of R134a from his exploded system, it is the same as producing 1430 lb of CO2, or (warning: chemistry babble ahoy!) about:

650kg of CO2 or
14800 mole of CO2 which requires about
1850 mole of C8H18 (which gasoline isn't, but close enough) which is
211 kg gasoline or about
310 liters of gasoline (with a SG=0.68) which is
82 US gallons or
2 fillups for a Ford Excursion.

It's all relative. Don't worry about fixing the AC. Worry about the Ford's.

First, I don't really like being addressed as "Dude". It is somewhat derogatory on forums.

Oh yes, you are right. One car isn't much. But there are 65 million cars in the US alone. If you want to pick and chose your data to justify your position, fine - but you should have compared one car to a coal-fired power plant. It makes taking personal responsibility look even more ridiculous.

But the fact remains that just because there are other, larger emitters of greenhouse gases it is poor justification to say "I can therefore do anything I want to". We all have a responsibility. I can't do a damned thing about coal-fired power plants or Ford Excursions, but I can do things that effect MY greenhouse emissions. One sure way to guarantee failure in achieving any goal is to say "I can't make it perfect immediately so I don't have to do anything at all".

[instarx]

Well....I'm not a chemist either! And, after reviewing my post, it seems that I do not have enough education to know when to properly use a 's...like after Fords!

The EPA book is interesting. As implied, one of the advantages of CFC's were their chemical stability. I really don't have the knowledge to intelligently comment about ODP or chemical stability of R22, but it almost looks like there may have been a double (or more) extrapolation based on observations. For example, for R12 the logic appears to be, chlorine attacks ozone, R12 has chlorine and is chemically stable so it will hang around, so R12 has a high ODP. R22 also has chlorine, but it is less chemically stable than R12, so at least it will go away, so R22 has some ODP but less than R12. But, it seems strange that the chemically stable compound (R12) will somehow provide more reactivity (from the Cl- ion) with greater ODP than the less chemically stable R22.

Lol, well oddly enough I am an Environmental Engineer. The GWP is a metric that takes all those time factors, degradation, mode of action, moisture interactions, oceanic sequestration rates, etc. into account when calculating a gas' effects on Global Warming. For example it takes into account that R22 has a 12 year life in the atmosphere while 134a has a 14 year life. It takes into account that r22 reaches high altitudes and damages the ozone layer while 134a doesn't, but also that 134a increases GW through mechanisms not available to R22. Listing things like that as being confounding factors isn't really valid since the GWP already includes them. The GWP was specifically created to normalize the evaluation of the global warming effects of gases no matter their pathways. This was done because deniers were doing what you just did - clouding the issue with seemingly relevant factors that seemed to cast doubt on the science but really did not. (not saying you are a GW denier - just that that is one of the techniques they use.)

And quite frankly, understanding what the numbers mean can often put things into perspective as far as what is relevant and what isn't. In my opinion, driving a 10 mpg vehicle is far worse than a little R134a venting. But, so some degree this is where we get into the sticky subject of politics and opinion vs science.

Again, just because something isn't the worst thing that could happen does not mean that it is insignificant and not worth correcting. Getting hit by a Mack truck is really bad - but it does not follow that getting hit by a Toyota is just fine. A Ford Excursion releases a lot of CO2 into the atmosphere - that does not mean it's perfectly fine to vent the greenhouse gas 134a to the atmosphere. That isn't science or "perspective".

Do I even have to comment on the contention that the GWP is suspect because of the number of significant figures used in a GWP value - and the conclusion that the people on the IPCC who created the GWP metric therefore can't be "real" scientists? Three significant figures in a GWP may very well be correct (and I suspect it is). The IPCC is extremely careful about such things simply because such a trivial mistake would open the entire report up to claims of it being false by the denier community (as you just did). But now that you mention it, the font used in the original IPCC report was sans serif. That should give anyone pause to question its validity.

Sorry about all the edits. They were done to reduce aggressiveness, improve wording and readability, and remove personalization in the original.

[abscate]

Let's wrap this up with

1.It's better to get your refrigerant evacuated than venting it to atmosphere.

I understand that cost, logistics, all play a factor here but if you can get this done, the planet appreciates it.

Without getting deep into science, the fact that it's only a small amount of refrigerant is NOT justification to think the impact is minimal. The nature of the photochemistry is such that these molecules act catalytically, which means they drive damaging reactions in the atmosphere without bring consumed.

2. It's better to repair your AC correctly and have no leaks than to feed it refrigerant.

[northernlights]

Lee, technically you are correct, R134a has very little effect on the ozone layer. But there is more to the story of R134a than ozone. R134a is moderate to strong greenhouse gas 1,400 times more potent than CO2. It has a GWP (Global Warming Potential) index of 1,430 which is only a bit less than HCFC-22, one of the worst of the old chlorinated fluorocarbons (GWP 1,800). Although it does not significantly deplete the ozone layer, it does contribute significantly to global warming through other greenhouse mechanisms. So the inference that most would make after reading your post -- that it is OK to release R134a directly to the atmosphere -- would be wrong.

Dude, you might want to park your car.

Assuming R134a has 1430x the GWP of CO2, means that if the OP manages to vent one pound of R134a from his exploded system, it is the same as producing 1430 lb of CO2, or (warning: chemistry babble ahoy!) about:

650kg of CO2 or
14800 mole of CO2 which requires about
1850 mole of C8H18 (which gasoline isn't, but close enough) which is
211 kg gasoline or about
310 liters of gasoline (with a SG=0.68) which is
82 US gallons or
2 fillups for a Ford Excursion.

It's all relative. Don't worry about fixing the AC. Worry about the Ford's.

First, I don't really like being addressed as "Dude". It is somewhat derogatory on forums.

Oh yes, you are right. One car isn't much. But there are 65 million cars in the US alone. If you want to pick and chose your data to justify your position, fine - but you should have compared one car to a coal-fired power plant. It makes taking personal responsibility look even more ridiculous.

But the fact remains that just because there are other, larger emitters of greenhouse gases it is poor justification to say "I can therefore do anything I want to". We all have a responsibility. I can't do a damned thing about coal-fired power plants or Ford Excursions, but I can do things that effect MY greenhouse emissions. One sure way to guarantee failure in achieving any goal is to say "I can't make it perfect immediately so I don't have to do anything at all".

Yikes, no insult intended, although I was definitely a bit snarky.

I'm a numbers guy, and that's all I was trying to illustrate, interjected with a bit of humor.

[instarx]

Yikes, no insult intended, although I was definitely a bit snarky.

I'm a numbers guy, and that's all I was trying to illustrate, interjected with a bit of humor.

No problem, I got a bit snarky too. Wait until you read the comment on your next post, lol. I apologize in advance.

[northernlights]

Yikes, no insult intended, although I was definitely a bit snarky.

I'm a numbers guy, and that's all I was trying to illustrate, interjected with a bit of humor.

No problem, I got a bit snarky too. Wait until you read the comment on your next post, lol. I apologize in advance.

Like the hockey guys say 'No blood, no foul!'

No worries!

[abscate]

One of the reasons it's great to moderate this site is guys like the two of you who deal with issues like adults. This is deeply appreciated. Ok, the free stick shift Volvos for life perk is okay, too.