Home Podcasts THMG017 – Meters IV: From Data to Action

THMG017 – Meters IV: From Data to Action


In this episode, Mike and Bob finish the meters series. We discuss what the mindset is from the point that you get a number on your display and the methods and reasons behind what to do.

Complete Show Notes

6:35 Recap of the First Three Metering Episodes

  • Basic (or primary) metering technologies – covered how they work and the pros and cons of each technology
    • Also covered PID – PID meters read VOC (volatile organic compounds)
    • These are substances that contain carbon and hydrogen that is in vapor or gas form (or at least moving in that direction (vaporizing))
    • These tend to be toxic compounds that mimic or interfere with our organic chemistry
  • Advanced (or secondary) metering technology – covered how they work and the pros and cons of each technology
  • Metering techniques – covered how we use meters, when we use them, proper methods of surveying, considerations for use, and how each meter gives us a piece of the bigger picture

10:30 Handling Different Scenarios

  • Dealing with inside incidents
    • We should talk to people, learn more about the location, ask if the HVAC has been isolated, figure out if there are victims, etc.
    • Inside incidents have less airflow and will confine and concentrate chemicals
    • You should also be cognizant that the acceptable levels for an inside incident may be different than levels for outside incidents – always check your SOP
    • Determine if VOC is a health issue – cleaners, detergents, and household chemicals can all be VOCs
    • Low VOC reading – VOC that are toxic and also have low PPM aren’t common in residential areas; a few PPM might not be worth emptying a building
    • High VOC reading – the need to protect people increases; many IDLH aren’t this high, but it’s important to consider long-term exposure
    • PIDs tend to react quickly – amount of time differs depending on whether you’re using diffusion mode or pump mode (affected by the time it takes for air to move up the tube)
    • Meter both high and low – most VOC are heavier than air, but there’s very little stratification between floor and ceiling (focus search on higher levels)
    • If you find a source, clean up liquids or stop gas leaks – then, try to vent the area
    • Once readings have dropped, stop ventilating and see if VOC returns – if it does, your cleanup wasn’t the issue
    • If you can’t find the source, don’t vent unless safety requires it – venting moves air around and can make it difficult to locate the source
    • Turning off air handling units may help reduce airflow – if VOC drops after turning off air handlers, it’s getting to the HVAC system somehow
    • Ask questions – is there work being done? Cleaning work is a common source, especially if they’re using paint, sealers, polish, etc.
    • Is anyone sick? This can include headache, vomiting, dizziness, etc. – do a property history on the patients and request EMS
    • Are there smells and odors? Can everyone smell it, or is it limited to a few people?
    • Is there a pattern with the odor? Is it a new smell, or something they’ve smelled before and are only reporting now?
    • Consider if the source is external – check around the building for unusual items and check the garbage
    • Try to map out areas of concentration – can we reoccupy if we couldn’t find anything?
  • Dealing with outside incidents
    • These can be a concern because the volume of product needed to get a reading outside needs to be substantial
    • Wind becomes an issue because it’s difficult to figure out where it came from and where it may be going
    • If there are high concentrations, you might need to evacuate people from the area
    • Finding and stopping the source of VOC is really the only thing you can do when you’re outside

28:00 Specific Gasses and How to Handle Them

  • These readings are taken on 4 or 5 gas meters or single gas meters
  • It’s important to have knowledge of the specific chemicals you’re dealing with
  • CO
    • CO is a product of combustion, so we can narrow our search to combustion objects
    • Anything that reacts with O2 to create heat is a concern – burners, ovens, water heaters, fireplaces, grills, etc.
    • Once the source is found, turn the item off, vent the space and wait for readings to drop, and stop the vent and see if the reading comes back
  • Sulfur dioxide and hydrogen sulfide
    • We know these as sewer gasses – they’re products of decomposition and bacteria breaking down waste
    • Commonly used in chemical suicides
    • Sewers are the most common source – look at plumbing pipes and plumbing traps
    • Plumbing traps are a bend in a pipe that traps water – this water prevents the sewer gasses from entering a building – if it’s dry, add water
    • Once the source is found and taken care of, shut the vent and see if the product returns
    • Sulfur dioxide has been used as a refrigerant, so check old refrigerators and burn up your sensors if there’s high exposure

35:40 How Different Chemical Readings Affect Our Actions

  • High O2
    • The most likely source is a tank – find the tank and shut it down, then vent and re-check
    • Remember that high O2 levels can be dangerous in several ways
  • Low O2
    • O2 usually leaves areas via displacement – most common reason is a leak of compressed gas or liquefied gas
    • Pipe ruptures also lead to leaks – anything that can produce a constant flow of gas for a significant amount of time
    • Liquids are rarely able to displace O2 – not impossible, but there needs to be a lot of liquid due to the fact that liquid must evaporate to become a vapor
    • Chemical reactions also contribute to low O2 levels – rust, biomass, areas of stagnant air, etc.
  • Chlorine
    • This is generally an industry gas, but facilities with indoor pools will have chemicals that trigger your chlorine meter
    • Typically stored in cylinders
  • Ammonia
    • Considered to be an industrial gas, but it can really be found everywhere
    • Anhydrous ammonia is stored in low pressure tanks in farming areas – it’s also used in cleaning supplies
    • Can also be used as a refrigerant – was popular years ago, but is making a comeback because it’s environmentally friendly
  • HCN
    • This is another common industry chemical that’s used in jewelry businesses and may be present in small manufacturing facilities
    • HCN is a product of combustion when dealing with burning plastics and chemicals containing nitrogens
  • Radiation
    • As long as the source isn’t in the air, this is pretty straightforward
    • Always be conscious of time, distance, and shielding
  • Chemical warfare
    • Many of these meters will alarm for cross-sensitivity
    • Figure out if there are any injuries and where the chemical is located

45:25 Other Common Chemicals You Should Meter

  • Organophosphates – these are the backbone of many chemical warfare agents and are also the basis of many pesticides and herbicides
  • Chances are, you’re getting a false reading, but you should still use the meter to find it
  • LEL – find and remove the source; when ventilating, remember that you don’t want to draw a possible flammable through a fan
  • It’s always important to know your cross-sensitivities and start by eliminating the chemical your meter is reading for
  • Then, use your meter and your understanding of cross-sensitivities to see the big picture
  • Always look for CO, acetylene, hydrogen (battery bank or acid metal reaction), too
  • 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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