Chapter 5. Chemical Safety in DIYbio

Courtney Webster

If chemical safety was modeled after economic policy, many biology labs would follow a laissez-faire approach. Don’t get me wrong—I don’t blame the biologists. I blame the “kit”-ification of most of their experiments. Calling something “Wash Buffer B” abstracts away from proper chemical names. If you have to dig through fine print to find the ingredients, you have no way of knowing how hazardous it might (or might not) be.

Many DIYbio labs don’t have to deal with chemical reagents, so biological safety[1] is the primary concern. But if you need more than ethanol and bleach to run a lab, you should know some basic chemical safety skills.

PPE: Personal Protective Equipment

The first step is (obviously) to protect yourself. If you’re handling a chemical, you should at least wear safety glasses and gloves. By the way, not all gloves are created equal. For aqueous (water-based) solutions, latex gloves work just fine. If you’re handling a powdery chemical or organic solvent, you’ll want nitrile gloves (which are more chemically resistant).[2]

Pro Tip

A chemical’s material safety data sheet (MSDS) specifies the best type and thickness of glove to use.

Rookie Tip

If the glove rips when you’re trying to put it on, it’s too thin.

Preferably, you’ll be wearing a lab coat as well. My lab coats testify with numerous spots and stains (and I’m a pretty careful chemist). If you’re working with particularly volatile, toxic, or smelly materials, using a chemical fume hood is a good idea.

Hazard Pictograms: The Primary Hazard of a Chemical

Let’s move on to the important stuff. If you have the name of a chemical (the real name), how can you tell if it is hazardous? The quickest indication will be a little picture on the bottle (a hazard pictogram).

Toxicity hazards

Next are fairly intuitive pictograms from OSHA’s website.[3] We’ll start with the health and contact hazard pictograms. Chemicals with minor[4] toxicities (irritants) will be labeled with the “warning” pictogram (sometimes represented with a large “X” instead of an exclamation point; see Figure 5-1). A corrosive pictogram is common for acids and bases, meaning you’ll get a chemical burn (a la Fight Club) if you spill it on your skin.

Toxicity pictograms I: avoid contact (irritant, corrosive)
Figure 5-1. Toxicity pictograms I: avoid contact (irritant, corrosive)

When you move into more serious territory, the pictograms distinguish between an acute (immediate) effect, indicated with a skull and crossbones, and a chronic effect, clearly represented by the person with the alien-like hole in his chest (see Figure 5-2). Chemicals with chronic toxicities are carcinogens, mutagens, sensitizers—generally nasty stuff. You might also see the “dangerous for the environment” pictogram, indicating the disposal of this chemical (and any waste containing this chemical) needs to be carefully managed. If it’s dangerous for the fishies, it’s dangerous for you.

Toxicity pictograms II: handle with extreme care (acute toxicity, chronic toxicity, dangerous for the environment)
Figure 5-2. Toxicity pictograms II: handle with extreme care (acute toxicity, chronic toxicity, dangerous for the environment)

Physical hazards

Moving on to physical hazards, you’ll often encounter the flammable pictogram (see Figure 5-3). Keep this away from your Bunsen burners and flame sterilization equipment. If you observe the explosive or oxidizing pictogram, you’ll want to get some trained advice on handling this material. It’s generally advised to keep any waste you generate containing oxidizers in its own waste container, as these can react with other common lab chemicals.

Physical hazards (flammable, explosive, oxidizing)
Figure 5-3. Physical hazards (flammable, explosive, oxidizing)

A pictogram will give you a quick indicator of the presence of a hazard, but it doesn’t provide hard guidelines on the scale of that hazard. If you like numbers (like me), you can take a look at the NFPA (National Fire Protection Association) rating.

NFPA: National Fire Protection Association (an Aggregate Safety Rating)

The NFPA gives you an overall rating of the chemical in each hazard category (health, fire, reactivity, and other specific hazards). The higher the number, the worse the hazard (see Figure 5-4).

You can (and should) make an NFPA label for your entire laboratory. It’s easy—for each category, find the chemical in your lab with the highest number in that category (health, fire, etc.) and put that number on your lab NFPA.

Pro Tip

If you have a DIYLab, you should make an NFPA sticker to indicate the overall hazard level for your entire laboratory. It should be posted on an exterior window in case of emergency.

If any of your chemicals contains a specific hazard (especially water-reactive or oxidizer), add those, too. This helps first responders prepare if there is an emergency in your lab.

Now we can identify the presence of a hazard with a pictogram and even get a feel for the scope of that hazard with an NFPA, but to get the full scoop on how to handle a chemical, you’ll need to look at its MSDS.

NFPA, deconstructed
Figure 5-4. NFPA, deconstructed

MSDS: Material Safety Data Sheet (Soon to Be Called SDS)

Any chemical you order should come with an MSDS. You can find them online (free of charge) as well. Rumor has it the name is changing from MSDS to simply SDS, so keep that in mind. If you search for this document using a chemical name (e.g., caffeine MSDS), it might be difficult to find the exact product you have—in that case, search the manufacturer’s website using the product number, or search using the CAS number of the chemical instead.

Pro Tip

You should keep a copy of the MSDS for every chemical you store in your laboratory.

Pro Tip

Read an MSDS before working with a new or unfamiliar chemical.

An MSDS will provide exhaustive information about the chemical at hand, but it won’t make it easy to glean the most important information (see Figure 5-5). On the plus side, it’s great for scary bedtime stories.

I’m not sure what’s worse—"POISON CENTER" in all caps, or the fact that this MSDS is seven pages long. The point here is that everything is a chemical and everything has a dose-dependent toxicity. Though it’s important to have a healthy fear of chemicals, you don’t need an all-encompassing, enclose-yourself-in-a-bubble kind of fear. So how do you take this long and technical document and whittle it down?

If you see toxicity pictograms, look for the words “fatal” or “very toxic” to indicate serious danger. (Note that caffeine simply said “harmful if swallowed,” not “toxic” or “very toxic.”) The "Toxicological Information" section will list an LD50 (acute toxicity) and any chronic hazards the chemical might have.

The MSDS for caffeine (found on Sigma-Aldrich)
Figure 5-5. The MSDS for caffeine (found on Sigma-Aldrich)

An LD50 provides a quantitative toxicity value. In general, the lower the initial number (the milligrams required to cause toxicity per kilogram of body weight), the more toxic the chemical. If you see materials with single- or double-digit LD50s, you should wear protective equipment and handle and dispose of these chemicals with extreme care.[5]

After checking acute toxicity, you want to look for chronic toxicity or other sensitivities. The following words should trigger some alarm bells: carcinogen, mutagen, teratogen, or sensitizer. In those cases, you’ll want to suit up well (gloves, goggles, lab coat) and use good lab technique to avoid any contact with the chemical (if you’re sure you have to use it at all).

Pro Tip

Keep a copy of the MSDS for every chemical in your lab (either in paper form or on a small USB drive). If you get exposed to a particular chemical, bring the MSDS with you when you seek medical treatment.

If you see flammability warnings, check out the "Physical and Chemical Properties" and "Stability and Reactivity" sections to determine boiling points and flash points. Be extremely careful if you see words like “flammable solid,” “ignites in contact with water,” or “handle under inert gas.” Have a trained chemist take a look, and see if you can avoid using this chemical altogether.

Ta Ta for Now

That’s it for basic chemical safety! Keep an eye out for upcoming safety topics (like chemical storage and waste disposal), and stay safe out there.


  1. The Occupational Health and Safety website is a gold standard for information on PPE, pictograms, and other lab safety tips.
  2. Sigma-Aldrich is my go-to website for MSDSs.

[4] Don’t take my word “minor” literally—read an MSDS to get an idea of the toxicity. Oh, you don’t know how to read an MSDS? Well it’s your lucky day—read on.

[5] For example, caffeine has an LD50 of 367.7 mg/kg with oral ingestion. While human LD50s aren’t provided (for obvious ethical reasons), you can generally assume that you and a rat will have a similar toxic reaction to a chemical. You simply scale the LD50 by weight to determine human toxicity. The average human weighs 154 lbs (or 70 kg). That means 50% of humans that ingest 25,739 mg of caffeine (25.7 grams, or 172 Starbucks lattes) might die. In comparison, the LD50 of sodium cyanide (a very toxic chemical) is 4.8 mg/kg for oral ingestion. That means a human would reach a possibly fatal toxicity level with only 336 mg (an amount that’s about a third of the size of an M&M).