In this episode, Mike and Bob discuss oxidizers are and how we interact with them.
Complete Show Notes
4:40 What is An Oxidizer?
- Part of a system known as a redox reaction or a reduction-oxidation reaction
- Specifically deals with the loss or gain or electrons – oxidizers are stronger than most other chemicals, so they just take what they want
- Elements are always trying to reach a neutral state, so when oxidizers take a chemical’s electrons, the chemical is no longer in a balanced, happy state
- Oxidizers either break the chemical apart or start to react with another chemical that it can get an electron from or give an electron to
7:35 NFPA Definition of Oxidizers
- “Any material that readily yields oxygen, or another oxidizing gas, or that readily reacts to promote or initiate combustion of combustible materials and can undergo a vigorous, self-sustained decomposition due to contamination or heat exposure”
8:05 “Any material that readily yields oxygen, or another oxidizing gas…”
- Many oxidizers contain oxygen and release that oxygen into the system when they react
- This can present the danger of oxygen enrichment and can change our LEL and UEL levels
- Also accelerates chemical reactions, which can be very dangerous
- Airborne oxidizers are difficult to control and can lead to unexpected reactions in other locations
10:05 “Or that readily reacts to promote or initiate combustion of combustible materials…”
- If enough heat is generated and oxygen becomes part of the reaction, we get fire
- This is one of the biggest dangers of an oxidizer – they have the potential to catch us off guard
- It can take a while to build up heat – from minutes to hours
12:45 “And can undergo a vigorous, self-sustained decomposition due to contamination or heat exposure.”
- This means the oxidizer can produce enough heat to break itself down
- Contaminants can be organic combustibles, which react to build heat and start a chain reaction
- Oxidizers are also light- and heat-sensitive and can be broken down by these factors
15:00 Where Can We Find Oxidizers?
- Anywhere – we all use oxidizers on a regular basis
- Residential settings – kitchen and bathroom – hydrogen peroxide, toothpaste, etc.
- Industrial settings – rocket fuel, stump removers, gunpowder, preservatives, etc.
- On the road – transported via DOT Classification 5 over the road trucks as a liquid or solid
17:25 How Do We Recognize an Oxidizer?
- From the chemical name – If it ends with “-ate,” “-ite,” or “-ide,” it’s more than likely an oxidizer
- Non-organic halogenated compounds
- Non-organic substances don’t contain carbon
- Halogenated compounds contain fluorine, bromine, chlorine, or iodine
- If you’re dealing with any of these substances, they’re oxidizers
- Treat the following as oxidizers: nitrites, nitrates, and peroxides
21:55 National Fire Protection Association (NFPA) Oxidizer Classifications
- Classes 1-4: the higher the number, the stronger the oxidizer and the greater likelihood of a reaction
- Class 1: No measureable increase in the burning rate of combustible materials it comes into contact with
- Class 2: Moderate increase in the burning rate of combustible materials it comes into contact with
- Class 3: Can undergo an explosive reaction due to the contamination or exposure to thermal or physical shock, severely increasing the burning rate of combustible materials it comes into contact with
- Class 4: Can undergo an explosive reaction due to contamination or exposure to thermal or physical shock, causing a severe increase in the burning rate of combustible materials it comes into contact with
23:50 Case Study: Texas City Disaster
- Texas City cargo ship caught fire in 1947 – responders originally thought it was a grain fire, so they tried to smother the fire when water didn’t work
- Ship detonated – took out the entire fire department, knocked a plane out of the air, and leveled half of the town
- Actual cargo was ammonium nitrate fertilizer, which is an oxidizer
26:30 Things to Consider
- Always identify the specific oxidizer you’re dealing with
- Recognize the possibility of a reaction or explosive hazard
- Evaluate the density of the material – the higher the density, the greater the risk of explosion
- Consider how much contamination got into the product that’s burning
- Think about the particle sizes – the smaller the particle, the greater the hazard
- Use copious amounts of water to cool off the material and halt the decomposition – keep runoff in mind, though
28:15 Extinguishing Fires
- Extinguishing agent you use can react with the oxidizer that’s present
- Dry Chem makes the fire worse – you can create an explosive byproduct
- O2 displacing agents also can’t be used because they create their own oxygen source and will continue to burn
- If you have a large fire, consider whether you’re in an indoor or outdoor environment – evacuate the area and allow a free burn
- Set up large caliber streams to throw large quantities of water over a long distance
- Remember that smoke is highly toxic, so use SCBA and set up your zones
29:40 Handling Spills
- What did the substance come into contact with? Did it mingle with things it doesn’t play nicely with?
- How strong is the oxidizer?
- Is the substance reacting? It might be giving off heat, releasing vapors, bursting into flames, etc.
- Will it react with metal?
- Are there contaminants in the over pack container? Consider flooding the over pack with water.
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- THMG095: Extinguishing Agents, Part III