I have been using and repairing Hottop Coffee Roasters for about twenty years. I have seen a few roasters that suffered a fire. Here are examples of the aftermath of two separate incidents:
In every case I have handled, the roasters which were involved in a bean fire were still operational. With little more than a basic cleanup these roasters (including the two seen above) were able to successfully roast coffee before any repairs were made. The top photo had beans ejected on fire and no water spray was available to put the fire out. In the bottom photo, no water was used that we could tell, but a dry chemical fire extinguisher was used. That mass of beans stuck in the drum reflects just how oily those beans were. The electrical as well as the emergency manual eject mechanisms were both working. The beans could not be ejected because they clogged the eject chute. How? The user turned away 'just for a moment' right at the end of the roast.
Roaster fires happen. But we can say with nearly 100% assurance that coffee roasters do not catch fire. But coffee beans being roasted can catch fire. Chaff can catch fire. The organic 'dust' and particulate matter which come from the beans can catch fire. The oils produced by the beans which become deposited on the inner surfaces of the roaster can catch fire. But coffee roasters do not catch fire. It can happen to even experienced roasters. I know. It has happened to me twice; both times were totally my fault.
It is much like the oven in your home. You can set it for 450 degrees and you can likely leave it for many hours without a problem. Put a chicken in the oven and set if for 450 degrees and leave it for hours and you find out if your smoke detectors are working, and possibly, how much a new oven costs.
But the basics are, with the proper maintenance and preventative care and a bit of diligence while roasting, you, your home, and your roaster can go a long way to be protected from damage caused by a fire. Here are some tips:
Read the owners manual! - The manual contains a lot of good information on roasting and what to expect in the various stages during a roast. Being able to predict what will happen will help you get the most out of the beans and avoid roasting problems. Even if you have been using a Hottop roaster for years, refresh your memory occasionally.
Maintenance - In the back of the manual there is a section called "Care and Cleaning." There is more to maintenance than just emptying the chaff tray and walking away from the roaster. The items there were written for a reason. Roast after roast, oils and debris can build up inside the roaster. In time, if left to build up, they will become a fire hazard.
Never leave a coffee roaster unattended during a roast - It is emblazoned all over the manual as well as right on the roaster itself. "In the room" is NOT the same as 'attended.' You need to be right there, at the control panel, watching the temperatures and looking into the roast chamber to observe the progress of the roast. You need to pay attention to the sounds the coffee makes while roasting, the color of the beans, and the volume and aroma of the smoke. Be ready to hit the eject button. Do not turn to watch TV or run to answer the phone and expect the automatic eject to finish the roast for you safely.
Weigh Your Coffee Accurately - We recommend roasting at least 250 grams of coffee each time. Do not use a kitchen scale that weighs in ounces. One ounce is about 28 grams. Roasting "about 7 ounces" can be 20% too little coffee and will dramatically increase the risk of burnt coffee, or worse. Even roasting 'about 8 ounces' can result in a roast progressing too quickly. Inexpensive gram scales can be had for relatively little cost compared to the value of a Hottop!
Avoid roasting very dark coffee - Hopefully you are buying quality green coffee and dark roasting removes much of the flavor you paid from the beans. As the beans become oily in a dark roast the risk of ignition greatly increases, but it also can lead to those beans sticking in the eject chute. A lot of bad things can happen at that point if you are not prepared.
Expect the best, but be prepared for the worst - If the beans have not ejected, unplug the roster. You want to keep the beans inside the roasting drum. Unplug the roaster from the outlet. With gloves on, simultaneously lift the bean loading chute cover no more then about 1/2 inch and using the hand-pump spray bottle of water (which the owner's manual states you should always have on hand when roasting), shoot a stream of water into the roast chamber. Pump the bottle many times, then put the chute cover back down. When water turns to steam it expands around 1700 times which removes heat from the burning beans and it displaces oxygen. Doing that once or twice should easily extinguish the fire.
To extinguish beans which ignite when ejected or get caught in the eject chute do the same thing- disconnect the roaster from the outlet, set the spray bottle on stream and shoot it right at the beans. If they have ejected and are burning in the cooling tray, use a wider spray pattern and spray freely until the fire is extinguished.
If done in the manner described there is little worry of damaging any internal components with the water. While I do not advise it, I have washed circuit boards with cleaning solutions and rinsed with water and they still operate just fine.
Cost? - Using the above tips and extinguishing a fire as described above usually just requires a user to clean the drum and front cover, then allow the roaster to dry out. If we have to repair a roaster that has seen an ignition event, the cost can run from around $300 and maybe as high as $1000 or more depending on what parts were damaged. The roaster has to be disassembled to a great extent and cleaned, and that takes time, and skilled labor is expensive. Being attentive when you roast costs nothing, and a spray bottle filled with water less than $5. It's your choice.