The cheaper one is an ABC Dry Chemical (most common extinguisher around). Halguard is Halotron (similar to now-banned Halon). Halotron is a clean agent which means it leaves no residue unlike the dry chem ones.The cheaper dry chem extinguishers cannot be refilled if they lose pressure, get used, etc. The good, reusable ones have a metal control head not plastic like the cheap ones. Both extinguisher types can be used on ABC fires. Halotron is awesome if you can afford it. But for the price of one Halotron you can get two reusable dry chems. The 20 buck ones are most likely one-time use. A refill/recharge on the good dry chems costs around $20 I believe, depends on the company, how much poweder, etc.
Not sure where to start. Halon\halotron or other similar extinguishers are used primarily for sensitive electrical equipment. ie computers. They are a clean agent and actually interrupt the chemical chain reaction and displace oxygen, but they provide little to no cooling effect. They are also highly toxic.
CO2 can be used similarly, but the low temperatures associated with CO2 can cause water vapor to form causing a short in highly sensitive electronics.
ABC extinguishers are the most common. Each unit of A rating has an equivalent of 1.25 gallons of water. The B rating corresponds to square footage of flammable liquid fire.
An ABC extinguisher is by far the best choice to carry on a vehicle. It has the ability to extinguish ordinary combustibles (a), flammable liquids (b), and energized electrical (c). The trade off is they are not great at anything and are quite messy with the powder discharge.
I suggest an abc extinguisher with a metal head because they can be serviced. Costco sells good larger extinguishers for around $30.
