PPM Calibration Gas - HVAC Service Business

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Discussion Overview

The discussion revolves around the calibration of electronic refrigerant detectors used in the HVAC service industry, specifically focusing on the methods of creating a calibration gas and the implications of different parts per million (PPM) definitions. Participants explore the accuracy and appropriateness of using homemade calibration gas for detecting refrigerant leaks.

Discussion Character

  • Exploratory, Technical explanation, Debate/contested

Main Points Raised

  • One participant describes their method of creating a calibration gas by mixing a known weight of refrigerant with a calculated weight of air, questioning its adequacy for calibration purposes.
  • Another participant notes that the definition of parts per million can vary (w/w, w/v, v/v) and suggests that the original approach is suitable for weight/weight ratios, while other definitions may require conversion factors.
  • Several participants express uncertainty about the clarity of their understanding regarding PPM, with one suggesting that PPM can also be interpreted as milligrams per liter.
  • A participant raises a concern about the accuracy of using simple gas weights compared to molecular weights, expressing a preference to avoid complex calculations involving moles and Avogadro's number.
  • One participant reiterates the definition of PPM in the context of water solutions, indicating that the mass of 1 liter can be approximated to 1 kg.

Areas of Agreement / Disagreement

Participants do not reach a consensus on the best method for calibration gas preparation or the most accurate definition of PPM, indicating that multiple competing views remain regarding the approaches and definitions discussed.

Contextual Notes

There are limitations regarding the assumptions made about gas behavior and the definitions of PPM, which may affect the accuracy of the calibration method. The discussion also reflects varying levels of comfort with chemistry concepts among participants.

Who May Find This Useful

HVAC professionals, technicians involved in refrigerant detection, and individuals interested in calibration methods for gas detection may find this discussion relevant.

Wayne3210
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TL;DR
µgm/gm PPM concentrations close enough?
Been a while since I was here...thanks in advance for any replies. :smile:

I'm in the HVAC service business and part of that "service" involves locating (or attempting to locate) refrigerant leaks. And that usually involves the use of some sort of electronic hand held detector. Thing is, not all detectors are the same and lately I've been comparing detector performance (sensitivity) via a "homemade" calibration gas.

The calibration gas is concocted by introducing a known weight (µgm) of a refrigerant into a bucket containing a calculated weight (gm) of air, based on published "normal" air conditions. So, my "defined" PPM ratio is µgm/gm.

Is that close enough for a backyard chemistry lab?
 
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A lot depends on a kind of ppm - it can be w/w, w/v or v/v. Your approach is perfect for w/w, other types will require some additional conversion factor.
 
Thanks...:wink:
 
Not sure if my understanding of the situation is clear, but parts per million can be taken as milligrams per liter.
 
symbolipoint said:
Not sure if my understanding of the situation is clear, but parts per million can be taken as milligrams per liter.

It's a matter of detecting a small amount of refrigerant vapor within the surrounding air space. The first time around, I think I used some unit of refrigerant weight relative to volume, never thinking in terms of weight to weight ratios. After more research, I read gas concentrations were better defined in terms of weight.

My concern is whether or not the method of simple gas weights is significantly less accurate than using molecular weights...I don't really want to deal with moles and Avogadro's number. I did pretty good in college physics but chemistry was not my strong suit... o0)

Thanks...
 
symbolipoint said:
Not sure if my understanding of the situation is clear, but parts per million can be taken as milligrams per liter.

That's w/v for water solutions (where mass of 1 L can be safely assumed to be close to 1 kg).
 

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