Home Podcasts THMG108 – Water-Reactive Substances

THMG108 – Water-Reactive Substances


In this episode, Bob and Mike discuss water-reactive substances and how they affect us as hazmat technicians.

Complete Show Notes

4:40 Why Do Some Substances React to Water?

  • A variety of reasons – all comes down to the fact that the overall energy of a system will be lower if it reacts with water (or even sometimes just the air)
  • However, not many air-reactive substances react with moisture – some react with O2, but some can be moisture in the air
  • Whether we’re sharing electrons or trying to find a lower energy state, two chemicals that want to react will come together – hazmat gets involved when they come together in an uncontrolled manner

6:35 How Do We Determine if a Substance is Water Reactive?

  • Check the SDS (safety data sheet) – look for Section 5, which is Fire and Explosion Data
  • Leaf through the green pages of the Emergency Response Guidebook (ERG) – sometimes nomenclature can reveal the possibility of water reactivity
  • Look for:
    • Alkali metals
    • Organometallics
    • Acyl chlorides
    • Main group metal halides
    • Metal oxides
    • Acid anhydrides
    • Nonmetal oxides
      • CO2 is a nonmetal oxide that does react with water – however, the reaction isn’t very exothermic, so it doesn’t give off a lot of energy – this is why we consider it to be compatible
  • Remember that these nomenclatures are guides, rather than rules – designed to make you stop and think before proceeding
  • The reverse is also true – just because something doesn’t fall into one of these nomenclature categories doesn’t mean it can’t be water reactive

10:35 Flammable Gasses from Water-Reactive Substances

  • Flammable gas – some products give off a flammable gas when in the presence of water
  • Examples:
    • Calcium carbide and water – when they come together, they create an extremely flammable gas called ethyne (AKA acetylene)
    • Beryllium carbide and water will produce methane
    • Calcium hydride and water produce hydrogen gas
  • The hazard itself isn’t a thermal reaction to water (doesn’t blow up or produce a fire), but it can give off a gas that produces a dangerous atmosphere
  • If water and the product you’re dealing with have mixed, what do we do?
    • Start by determining what the product is – remember that the hazard is the product, not the original chemical
    • Figure out if the reaction is done – if it isn’t, can you stop it?
    • Determine whether the gas is going up or down
    • Figure out whether there are ignition sources
    • Find out if you can ventilate and meter properly

15:30 Toxic Gasses from Water-Reactive Substances

  • Some metals will produce ammonia when paired with nitrogen (i.e. lithium nitride)
  • Other types produce even more extreme toxic substances like phosphine gas – this is produced when aluminum phosphide comes into contact with water
  • You can easily protect yourself with your SCBA – very few of these substances are toxic via transdermal
  • Always make sure people without SCBA are safe
  • Determine what the product is from people who witnessed the reaction so you know how to meter for it
  • Have your PID, FID, Dräger tubes, chips, etc. handy

20:45 Determine the Extent of the Reaction by Asking Questions

  • How much product has come into contact with how much water?
  • How long will it continue to react?
  • Can you separate the unreacted product?
  • Can you provide safe ventilation?
    • This is important because you need to know where you’re sending the toxic material
  • Is the substance corrosive?
    • When a water-reactive material creates a corrosive, it can produce either a gas or a solution

24:45 Thermal Reactions from Water-Reactive Substances

  • Product catches on fire – fire departments usually deal with this before hazmat arrives, though

29:50 Mike’s Scenario for Bob: Dealing with Water-Reactive Stuff

  • A student has dropped a glass jar of a water-reactive substance into a metal sink at a local college
  • You see a chunk of substance that’s obviously reacting when you arrive on-scene
  • Nobody was injured, so you can easily gather information from witnesses and the student themselves
  • Have your 4 gas meter with you and your PID – also have pH, KI, and F papers and your freon detector
  • Work your way into the room slowly – start at the doorway and take your time as you move towards the sink
  • Wear bunker gear and SCBA until you have reason to do otherwise – better safe than sorry
  • If necessary, foam the room to stop vapor production
  • Always remember that a hazmat isn’t a big deal if it’s in its container

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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