Home Ask The Haz Mat Guys ATHMG003 – Ask the Haz Mat Guys, Episode III

ATHMG003 – Ask the Haz Mat Guys, Episode III


In this episode, we answer the following questions:

  • How does humidity affect our metering devices?
  • Why can’t we calculate water density using molecular weight?
  • Can we transport a leaking vessel containing a hazmat?
  • If alpha radiation is blocked by the skin, how do we know if it’s inside us?

Complete Show Notes

00:55 Question #1 – How Does Humidity Affect Our Metering Devices?

  • Humidity has the most significant negative effect on photoionization detectors – very high humidity decreases their sensitivity
  • Some detector tubes lose sensitivity because the humidity interferes with the chemical reaction taking place in the tube
  • Many types of tubes come with a humidity “correction” chart, which allows you to modify the readings under a different humidity condition – be sure to review the operating manual
  • Calibration checks help assess the effects of temperature, humidity, and barometric pressure on each particular meter – perform calibrations in the same environmental conditions the meter will be used in

2:30 Question #2 – Why Can’t We Calculate Water Density Using Molecular Weight?

  • Molecular weight is used in air because it’s usually very thin – allows us to determine the actual physical weight of a product and compare it to the weight of air (29)
  • If it’s more than 29, the product sinks, and if it’s less than 29, the product rises
  • Doesn’t work with water because even dense products (like huge steel ships) can float
  • When you compare the total volume of the heavy object (i.e. a ship) with the total volume of water that it’s displacing, the ship is lighter
  • You may have a very large, heavy molecule, but if its weight per unit volume is less than water, it floats
  • Molecular weight almost always shows something as sinking, but this isn’t the case with a lot of heavy molecules out there (most of them float)

6:10 Question #3 – Can We Transport a Leaking Vessel Containing a Hazmat?

  • Check out 49 CFR (Code of Federal Regulations), which handles DOT commerce rules and regulations
  • 173.301a2 – “A cylinder that has a crack or a leak, is bulged, has a defective valve, has a leaking defective pressure valve, or bears evidence of physical abuse, fire, or heat damage, or has detrimental rusting or corrosion may not be filled or offered transportation”
  • Bob contacted Mike Moore from STTS for more information
    • Yes, we can transport a leaking hazmat vessel
    • However, it must be escorted by state or local law enforcement
    • Ask yourself:
      • What’s the rate of the leaking material?
      • Is the leaking material a product that will immediately vaporize to a gas?
      • What are the vapor densities – heavier or lighter than air?
      • Is the material liquid?
      • Can the material be temporarily captured in an absorbent patch?
  • Most commercial motor vehicles with a LP motor tank are mounted low – allows the gasses to fall to the ground without passing through or around the vehicle
  • Vehicles using LNG usually have tanks that are mounted high – allows the gasses to float away without passing through or around the vehicle
  • Emergency responders have to be familiar with the fuel systems and emergency loading and unloading features of these systems
  • Always check with your AHJ (authority having jurisdiction) for more details

9:35 Question #4 – If Alpha Radiation is Blocked by the Skin, How Do We Know If It’s Inside Us?

  • If it’s strictly an alpha source, there’s no way to determine if you’ve been contaminated
  • Hardly anything in the world only gives off alpha radiation, though
  • On the other hand, almost anything that gives off radiation produces alpha, beta, and gamma rays (which go right through the skin)
  • This means you can assume you’ve been exposed to alpha radiation if you’ve been exposed to beta or gamma rays – this is an example of dual/multiple signatures

Have a question? Send an email to feedback@thehazmatguys.com or leave a message on our Haz Mat Guys comment hotline: 843-628-1484

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