Blue

Health:
4-Extremely poisonous
3-Poisonous
2-Moderately toxic
1-Slightly toxic
0-Non-toxic

Red

Fire Hazard:
4-Very Flammable
3-Readily Ignitable
2-Ignited with heat
1-Combustible
0-Will not burn

Yellow

Reactivity Hazard:
4-May easily Detonate (explode)
3-Shock & Heat may detonate
2-Violent chemical change
1-Unstable if heated
0-Stable

White

Specific Hazard:
OXY– Oxidizer (Concentrated source of oxygen or something that behaves like oxygen.  Causes combustible material to more easily catch fire.)
ACID – acid
ALK – Alkali (corrosive to skin, reacts violently with acidic material)
COR – Corrosive
W – Use no water

The health and fire hazard warnings are self-explanatory. The Reactivity Hazard is mostly looking at high speed reactions which can make it explode. Other types of reactivity may be indicated in the Specific Hazard diamond.

NOTE: In chemistry labs, these 4 colors are often printed on chemical containers as bars instead of a diamond; however, they have the same basic meaning.

OXY means that it can be a source of oxygen or have elements that will behave like oxygen. The chemicals don't burn themselves but speed up the burning of other chemicals. For example, potassium chlorate when heated releases oxygen atoms. When this happens, simple things like paper, plastic, wood, sugar, coins, and oil will burn white hot like a flare and could explode.

Elements that behave like oxygen are chlorine, fluorine, iodine, and bromine.   They would have the OXY label on them.  Like oxygen, they have a strong tendency to rip electrons off of other atoms.  So items that burn in the presence of oxygen would also burn in the presence of these listed elements.

ALK means that the chemical is alkaline which means the opposite of acid but just as dangerous. The word "alkaline" comes from the name of a plant that grows next to salty lakes or oceans. In Arabic, it's called "Al Kali" or the saltwort plant. The ashes of this plant neutralizes acids. That is why chemicals that neutralize acids are called alkaline.

Strong alkaline chemicals are especially corrosive to skin (it turns the fat in skin into soap). Alkaline chemicals neutralize acids but in the process can put out tremendous amounts of heat that can start fires and generate gases that can build up explosive pressures. Common alkaline chemicals are ammonia (a gas used in agriculture), cleaning ammonia (ammonium hydroxide), and sodium hydroxide (Drano drain opener, Easy Off oven cleaner & Red Devil soap making Lye). These chemicals can be dangerous by themselves but can also generate a lot of heat when mixed with acids.

COR means that the chemical is corrosive but not because of acid or alkaline properties. It might be corrosive because of it reacts violently with water or if exposed to the moisture in skin, damages skin. Chemicals used in the computer chip industry like phosphorus trichloride, boron trichloride, aluminum trichloride, and silicon tetrachloride are in this category.

Picture is a leak from a truck carrying 12 tons of phosphorous trichloride, which has the NFPA warning of Health=4 (deadly), flammability=0 (non-flammable), reactivity=2 (violent chemical change). The Specific Hazard is listed a Water Reactive. In contact with water (in tissue or with liquid water) it creates hydrochloric acid and phosphoric acid.  

EASY OFF OVEN CLEANER: This is not in the kit but may be in your kitchen. One MSDS gives the rating of 3 for health, which is extreme danger (see diamond). It also states, "Inhalation: Not toxic by inhalation. Eye Contact: Corrosive to eyes. Skin Contact: Corrosive to skin. Signs and symptoms of overexposure include reddening of skin, tissue destruction, delayed pain. Ingestion: Not orally toxic; however, product is corrosive to mucosal membranes."

In this case, the MSDS is not exaggerating. One ingredient at 5% concentration is sodium hydroxide, which is quite corrosive, especially to the skin and eyes. The warning on the label on the can says to wear gloves, but it would also be a very good idea to wear goggles as well because it can easily cause blindness.

A web site that has the MSDS for many household products is
http://householdproducts.nlm.nih.gov/
Be sure to visit it.

SODIUM POLYACRYLATE :  This chemical used as a soil substitute and used where water needs to be absorbed like in diapers. 

As you can see from the NFPA sign the chemical is safe in all three areas: Health, flammability, and reactivity (explosiveness). One MSDS publisher does say it can be irritating to skin or eyes. (but that's about true of about any powder).

POTASSIUM IODIDE (KI):  This iodine salt is sometimes sold as "radiation" pills.   That's because nuclear bomb fallout often contains radioactive iodine.  The claim of this pill is that if you ingest extra iodine by taking these pills, your body won't try to absorb the radioactive iodine that will be in the environment after a nuclear bomb.   

The NFPA sign for potassium iodide shows Health=1, Flammability=0, Reactivity=1.  The MSDS information says "Skin Contact: may irritate", "Eyes: may irritate", "Ingestion:  Large doses may irritate GI tract so induce vomiting", "Inhalation:  irritation, coughing, sore throat, and labored breathing."

FIRE SAFETY:  Getting burned or setting something on fire is a major concern. 

Some portable lab kits have an alcohol burner that is made of metal so it won't break, but metal conducts heat so it will get hot.  Also, the metal stand where a beaker or container is placed will also get hot.  The problem with hot items is that they don't look hot unless they are glowing.

Alcohol burns very cleanly so you can hardly see the flames. If the alcohol spills and catches on fire, you may not even see the flames.      So that means you have to be more careful than normal around alcohol and an alcohol flame. 

Notice the metal tongs in the image. If you have those, use them to keep from burning your fingers or wait until the items cool.

GLASSWARE SAFETY: Glass is resistant to chemicals and heat, so it's a common item in labs. But as you know, when glass breaks, it can cut you.  Your kit may have several items that are made of glass including a long glass thermometer, which is probably the easiest item to break.  So be extra careful with the thermometers.  

Graduated cylinders are usually made of glass, but most portable kits choose plastic ones for extra safety.   However, some items like beakers, Erlenmyer flasks, and a few other items are usually made of glass. 

CHEMICAL SAFETY:  Most chemicals in portable kits for home use are fairly safe to be around, but that doesn't mean they are necessarily safe to touch, taste, or even smell.  For example, you have worked with gasoline, which is considered quite dangerous, but if you don't expose the gas to a flame, taste it, or inhale it, then you can handle it safely.  So working with chemicals in your kit is like that. They are fine if you avoid contact with them.

Gloves are included in the kit for the times your will be working with chemicals that are not good to contact.

EYE SAFETY:  Your eyes are the most vulnerable part of your body and the most important.   Your kit has goggles for eye protection.  The lab instructions will remind you when goggles are needed. 

Chemical Splash Goggles are made to resist liquid splashes to the eyes.  Normal glasses or other kinds of safety glasses are more comfortable but not as good at stopping liquid from getting in the eyes.