Calculating CO2 Concentration For Pepper Spray Devices

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Discussion Overview

The discussion revolves around the calculation of CO2 concentration in pepper spray devices, particularly focusing on the propellant used and the formulas required for determining the necessary amounts. The scope includes aspects of aerosol science and practical applications in consumer products.

Discussion Character

  • Exploratory
  • Technical explanation
  • Debate/contested

Main Points Raised

  • One participant mentions that liquid CO2 is used as a propellant in pepper spray devices but questions how to calculate its concentration.
  • Another participant suggests that liquid CO2 is unlikely to be referenced, as it requires very low temperatures, and typically dewars are used for that purpose.
  • A participant seeks clarification on how to determine the amount of propellant needed, noting that sprays typically last for a maximum of 10 seconds.
  • There is a distinction made between concentration and amount, with a participant emphasizing that these terms should not be used interchangeably in the context of the inquiry.
  • One participant asserts that liquid CO2 can exist at room temperature under high pressure, referencing its use in seltzer bottles and pellet guns, while also mentioning the solid state of CO2 requires lower temperatures.
  • Another participant suggests that liquid nitrogen might be used in some aerosol applications, such as spray cream.

Areas of Agreement / Disagreement

Participants express differing views on the use of liquid CO2 in pepper spray devices and the terminology surrounding concentration versus amount. The discussion remains unresolved regarding the specific calculations needed for CO2 concentration.

Contextual Notes

There are limitations regarding the assumptions made about the state of CO2 and the definitions of concentration and amount, which may affect the clarity of the inquiry.

mzuern
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TL;DR
I have a kid who wants to do a report on aerosols.
I have a kid who wants to do a report on aerosols. As I understand, we have researched that for pepper spray devices liquid CO2 is used as a propellant, but we can't find out how they calculate the concentration. Is there a place we can find the right formulas needed?
 
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mzuern said:
Summary:: I have a kid who wants to do a report on aerosols.

I have a kid who wants to do a report on aerosols. As I understand, we have researched that for pepper spray devices liquid CO2 is used as a propellant, but we can't find out how they calculate the concentration. Is there a place we can find the right formulas needed?
Welcome to PF.

It's unlikely that they referenced liquid CO2, since that requires very low temperatures and typically dewars are used for that, not spray cans

Please post links to the reading that you've been doing. Thanks.
 
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My mistake. It isn't liquid, but still how does someone determine how much is needed. Typically I think it only sprays for a maximum of 10 seconds. Is there a formula or ratio to determine amount needed?
 
Please post links to the reading you've been doing about this. Thanks.
 
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mzuern said:
we can't find out how they calculate the concentration
mzuern said:
Is there a formula or ratio to determine amount needed?

You seem to be using concentration and amount interchangeably - these are two different things, they mean different things and they can't be used freely one in place of the other (especially in the context of a school science project).

Please elaborate on what you want to find (and about the sources you consulted). It will really help us understand what you are looking for, right now we can only guess.
 
Liquid CO2 is pretty common at room temperature (and 80'ish bar IIRC) : that's the contents of the little tanks for seltzer bottles and some pellet guns ; it's the solid state that requires a low'ish temperature.

CO2 phase diagram

Maybe liquid nitrogen, which is used in spray cream, I think.
 

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