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
- 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
- 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
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