Assessing fire hazard of compounds

Question

Following up on a somewhat too broad question about amateur chemist safety, this will be the first to address some of the issues discussed there.

I often use the NOAA MSDS database (material safety data sheet) to investigate the chemicals I'm working with (they also have a nice reactivity predictor). As an example, let us examine the compound cyclohexylamine (I chose this as leading example for these followup question, because of the availability of extensive research in my country)

sometimes used as a plasticizer or catalyst. As an amateur I would carefully go through the MSDS and notice for example that it is flammable, caustic compound, scoring a 3 on flammability and health in the NFPA 704 hazard diamond.

As an amateur hobby chemist without all comfort of a basic lab (aside from safety goggles, gloves, lab coat, fire blanket), how would I judge if I can safely handle this compound with regard to its flammability, aside from conforming to the Protective Clothing section?

For example, I could imagine that flammable liquids with high vapor pressure (11 mm Hg for cyclohexylamine according to NOAA, I guess this is measured at a standard temperature as vapor pressure varies with temperature) or low auto ignition points (560 ° F) or low boiling points (274.1 °F) are unsafe for amateurs. Are there empirical (or theoretical) recommendation considering vapor pressure and ignition points, i.e., starting at what value will these factors become too dangerous for the compound to be handled in a relatively amateurish lab.

(I understand that the answers will be partly subjective, as for all answers regarding safety, but please try to give an objective as possible answer, preferably referring to external sources)

Answer 1

I guess I don't completely agree with the premise of your question. Gasoline is highly flammable, even potentially explosive, yet "amateurs" deal with it constantly. The key is that it is stored and used properly, from the pump to your gas tank. It becomes less safe if you pump it into a gas can, but gas cans also have certain requirements for storage safety.

So I think the issue may be what sorts of flammables would an amateur have a high chance of storing or using inappropriately. For example, any pyrophoric compound would be a good candidate to avoid, as most require a way to exclude air and moisture, which often requires specialist equipment.

Solvents with low flash points and high vapor pressure should also be treated with respect, but rubbing alcohol (isopropanol) or acetone might qualify for that designation. Storage in airtight fireproof containers in cool and dry places is often sufficient. Better yet, use a flammables cabinet. This simple step is something an amateur might skip for cost, but it may be the most sensible precaution. I have flammables cabinets, and I use them for ordinary hardware solvents along with experimental chemicals.

Finally, work safely! No flames, as they say in organic chemistry. Use hotplates or heating mantles rather than burners. If you must use flames for some reason, put away all flammables and keep them a safe distance. Pay careful attention to any spills and attend to them immediately before resuming work. And perhaps key for amateurs, small quantities! No need for an amateur to have gallons of flammables on hand. Even professional labs are trying to reduce quantities in the name of green chemistry.

EDIT: My go-to source for using and disposing of hazardous chemicals is Hazardous Laboratory Chemicals Disposal Guide by Margaret-Ann Armour. In addition to disposal techniques, each chemical has an extensive incompatibility section about what combinations can make a chemical even more hazardous, and all these entries have literature references. I use this book literally every time I do an experiment. It deals with much more than flammables, but flammables are definitely present.

Answer 2

Here is an illustrating link: http://www2.galcit.caltech.edu/EDL/public/flammability/USBM-680.pdf I hope it has a good analysis of what you want.

Answer 3

Two good comments others made:

1. Avoid pyrophorics
2. Avoid open flames
3. Work in a very well ventilated space (outdoors if necessary)

I'd add the following:

• Use the smallest quantities necessary
• Use the lowest concentrations necessary
• Keep a fire extinguisher nearby if working with anything flammable

Also, don't get too caught up in the NFPA labeling. The information there is primarily meant to communicate hazards to first responders. Instead, read through the Safety Data Sheet and look for information on the types of hazards associated with the chemical, as well as the recommended personal protective equipment.

A potentially useful resource is the ILO Chemical Toolkit. This is meant primarily for small and medium enterprises, but will help you to get a sense of the controls that would be considered necessary in industry. At the hobby level, you can certainly scale down accordingly - just be aware that working with hazardous substances is inherently risky and it's up to you to be aware of and to manage/mitigate that risk.