PPM Calibration Gas - HVAC Service Business

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The discussion focuses on the challenges of calibrating electronic refrigerant leak detectors in the HVAC service industry. The user is experimenting with a homemade calibration gas by mixing a known weight of refrigerant with a calculated weight of air to establish a parts per million (PPM) ratio. They express uncertainty about the accuracy of using weight-to-weight ratios compared to molecular weights for detecting small amounts of refrigerant vapor in air. The conversation highlights the importance of understanding different PPM definitions, including weight/weight (w/w), weight/volume (w/v), and volume/volume (v/v), and notes that while the current method may work for w/w, other types may require additional conversion factors. The user seeks clarification on whether their approach is sufficiently accurate without delving into more complex chemistry concepts like moles and Avogadro's number.
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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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