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Danger Signs In The Laboratory, Workplace and Hospital

Updated on August 1, 2014
susi10 profile image

Susan is a science geek, and if that wasn't enough, she gets all nerdy over technology too. She's also a writer.

Danger Signs

Danger signs indicate the many dangers that you would be expected to find in the laboratory, hospital or workplace. It is very important to understand these danger signs so that you will know what they mean and what precautions you need to take whether you are working in a laboratory, hospital or dangerous work area. The common workplace today especially in the manufacturing, health and medical industry is teeming with hazards from apparatus to chemicals. Working with these can prove very risky, so it is always helpful to know all the precautions you can take to protect yourself from these dangers. The best way to empower yourself with the knowledge is by checking all the danger signs associated with substances, chemicals and apparatus.

This guide has over twenty danger signs fully explained which are commonly found all over the world.

Irritant or Harmful

This danger sign is perhaps the most common of all because most substances in laboratories and hospitals have this sign. When you see this sign on a substance, it means that the substance may irritate your skin causing redness and itchiness. If this substance comes in contact with your skin, it could cause:

  • A severe redness on the skin
  • Cracking and dryness
  • Itchiness
  • Damage to the eye

To avoid this from occurring, you can precaution yourself by wearing gloves, working slower with irritant chemicals and keeping safety goggles on the eyes. These kind of precautions may seem very obvious but did you know that work-related skin problems are the most reported non-injury by workers in America? Long-term skin problems can results from short contact with irritant chemicals.

If you come in contact with an irritant chemical, wash with cold water immediately to prevent further damage and dilute the chemical.

There are two variations of this sign; irritant or harmful. They both mean the same thing and have the same effects. A sign with a large X and an 'i' in the bottom right corner means irritant whilst the sign without is harmful.


This sign can be identified with a large black flame on an orange background. Substances like these often include chemicals that do not necessarily have to be found in the workplace. Aerosols and other compressed cans can be highly flammable and must be handled with great care.

The flammability of a substance is the degree of difficulty it is to start combustion with a substance. This degree is found through fire testing and the result is documented in many safety codes and government regulations. The standard grades of flammability can be found in the table below.

Flammable substances start a flame very easily under normal conditions. Compared to other substances, they can start a fire much quicker than those that don't have this sign. To precaution yourself, follow your workplaces instructions as there are specific rules associated with various workplaces.

This list shows (but not limited to) some common highly flammable substances. These include:

  • Rubber
  • Ethanol (Alcohol)
  • Methanol
  • Wood
  • Gasoline (Petrol)
  • Acetone (found in nail polish remover)

Categories of Flammability

Easy or Difficult to Ignite?
100% Non-combustible, Material will never burn
Water, Carbon Dioxide (used in fire extinguishers)
Needs to be pre-heated to burn
Cooking oils, Lubricating Oils
Difficult to ignite
Will ignite under any temperature conditions
Ethanol, Acetone
Substance needs to be dispersed in air and rapidly vapourizes at normal atmospheric pressure
Natural gas, Butane, Propane

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A substance that is corrosive will burn human skin very severely and will destroy any material that comes in contact with it. These substances may also corrode metal, plastic and anything which comes in contact with them.

The word corrosive derives from the Latin word "corrodere" which means "to gnaw". This derivative fits the word perfectly as it gnaws or destroys anything in its path. To protect yourself form corrosive substances, always make sure that you check for this danger sign on all substance labelling. Wear gloves, a face mask, eye goggles and a laboratory coat to protect yourself from corrosive substances.

Many people confuse acids and bases by saying that just acids are corrosive and that bases are not. This is not true and must not be confused! Both acids and bases are corrosive, this can be seen on the pH scale.

List of Corrosive Substances

This list refers (but is not limited to) substances which are labelled as corrosive. Make sure to keep an eye out for these especially in the laboratory!

  • Strong Acids - Nitric Acid, Hydrochloric Acid, Sulphuric Acid (found in car batteries)
  • Super acids - These are extremely strong acids which are not very common.
  • Concentrated acids with a higher pH - eg: Acetic acid or formic acid
  • Strong bases, alkalis or caustics - eg: Sodium Hydroxide (used in soap)
  • Hydrogen Peroxide

You should consult Material Data Safety Sheets for more information on the specific corrosive substance you are referring to. This sheet should give you detailed information on all danger signs associated with it.

Dangerous To Environment

This sign means that this substance will cause damage to the environment such as fish, aquatic species and natural organisms. For example, if you throw a substance with this danger sign in the water, it could kill fish and other species which are living in the water.

Always make sure to dispose of these chemicals carefully and mindfully, knowing that any contact with the outside world could cause damage.Your local council may be able to dispose these substances safely for you, simply ask to see if it is possible.


If you ingest, inhale or otherwise make contact with these substances, they can cause serious damage from serious injury to instant death.

To precaution yourself against these chemicals, do not in any circumstances ingest or inhale these substances. Doing so could damage your internal organs, respiratory system or death. Wear all relevant safety equipment and make sure to check the Material Data Safety Sheets of all chemicals you are using.


An explosive substance is not commonly found in the workplace or laboratory simply because the huge danger it poses to storing it. These substances have masses of energy to exert and any shock to the chemical can release this energy. That equals an explosion.

Keep these substances away from heat, fire and never drop or exert pressure on them. Because of their huge danger, it is advised to work under the supervision of a safety instructor when handling these.


An oxidizing substance is one which releases large amounts of heat when it comes in contact with other substances. These substances do not pose much of a danger by themselves but pay particular attention when mixing chemicals together, or getting them involved in a chemical reaction. This is when the oxidation kicks in - releasing much heat.

When you see a substance labelled with this sign, what do you do? Firstly, wear all relevant safety equipment (especially gloves for hand protection. The oxidizing substance may react causing much heat to the hands) and make sure to have a fire blanket available in the workplace. Check a MDSS for more information on what specific chemicals will fulfil the oxidizing reaction with the chemical you are checking.

Always be careful when reacting an oxidizing chemical and a flammable chemical together - it could lead to fire.


As the name suggests, a biohazard is a living organism or tissue which poses a danger to humans if they come in contact with it. You may catch a contagious disease by coming in contact with the substance, or get a virus. These biological organisms come in a range of shapes and sizes from viruses to living tissue to contagious microorganisms to harmful bacteria. Biohazards are most commonly found in hospitals and in biological laboratories, especially clinical laboratories which deal with human tissue and blood samples on a daily basis.

Always wear a face mask, lab coat, eye goggles and gloves to fully shield yourself from the substance. Don't come in contact with it unless you truly need to - do so whilst following all safety procedures. Dispose of hypodermic needles in a sharps container, you will notice that there will be a biohazard sign on the front of the box.

High Voltage

This sign indicates high voltage, at such a high level that it could cause death. This sign is mainly found in industrial workplaces where high power is needed. Keep away from areas with this sign as it means that electricity is flowing at high voltage through the area. It is debated how much "high voltage" is considered to be, the IET finds that it is 1000 Volts whilst others say 35,000 volts(on electric transmission sites).

Protect yourself by wearing extra clothing that insulates rather than conducts. Stay away from all areas with this sign!

Click thumbnail to view full-size
Do not drink this water. It is "non-potable".Don't eat or drink in this area. Do not enter. Only for employees or staff.Do not touch. It could burn, cause damage or severe injury. No open flames should be near this area. Explosive chemicals or natural gas may be in this area.
Do not drink this water. It is "non-potable".
Do not drink this water. It is "non-potable".
Don't eat or drink in this area.
Don't eat or drink in this area.
Do not enter. Only for employees or staff.
Do not enter. Only for employees or staff.
Do not touch. It could burn, cause damage or severe injury.
Do not touch. It could burn, cause damage or severe injury.
No open flames should be near this area. Explosive chemicals or natural gas may be in this area.
No open flames should be near this area. Explosive chemicals or natural gas may be in this area.

Prohibition Signs

Prohibition signs are commonly found on construction sites which have loud noise, flammable substances on sight and toxic fumes. These signs prohibit you to do certain tasks. Let's take a look at some of them.

  • No Open Flames
  • Non-Drinking Water
  • Do Not Enter
  • Do Not Eat or Drink
  • Do Not Touch

© 2014 Susan W


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    • susi10 profile imageAUTHOR

      Susan W 

      6 years ago from The British Isles, Europe

      Flourish - Thanks for sharing your experience and thoughtful insight. I totally agree that people should check MSDSs for the chemicals that they are dealing with. I find them very useful when dealing with chemicals in the lab for detailing specific safety precautions and so forth.

      People usually laugh when they read these kinds of hubs, because not that many people deal with chemicals on a daily basis. But even simple household chemicals can pose threats. Weak acids such as lemon juice and vinegar can cause permanent damage to the cornea in the eye, if not treated. You are so right, the stuff in those sheets really do surprise you!

    • FlourishAnyway profile image


      6 years ago from USA

      With my husband being a chemical engineer and in sales, we have all kinds of industrial chemicals with some of these nifty labels FedExed to the house. Of course, I make him take them elsewhere ASAP. This is a helpful hub. People should consult their MSDS if they have questions on what they're dealing with. Some of the stuff in those MSDSs even for common household chemicals might surprise you.

    • susi10 profile imageAUTHOR

      Susan W 

      6 years ago from The British Isles, Europe

      Laila - Wow, thanks for sharing your experiences in the lab. It seems that without being cautious, the lab can be a very dangerous place. I'm so glad that nothing severe happened with the hydrobromic acid, that doesn't sound like the best thing to happen in a lab! I gained more insight into lab dangers with your comment, so thank you very much! :)

    • susi10 profile imageAUTHOR

      Susan W 

      6 years ago from The British Isles, Europe

      Amanda - I'm so glad that this hub explained some of the signs you didn't know. Whilst some are self-explanatory, there are a few that can be hard to guess (such as biohazard). Thanks for following me too, I really appreciate it! Great to see you are on the HubChallenge too.

    • susi10 profile imageAUTHOR

      Susan W 

      6 years ago from The British Isles, Europe

      John - Thanks for reading this hub and for the great comments. :-) Always appreciated. Yes, I agree. Most signs are very self-explanatory and they are designed for easy understanding. For me, the hardest one to guess is the biohazard sign. But once you know what it means, it is easy to recall.

    • LailaK profile image


      6 years ago from Atlanta, Georgia

      In my organic chemistry lab, I can't tell you how many times we had our skin irritate and itch, but we still ignored all these danger signs. Once my lab partner braught the hydrobromic acid bottle uncovered (when he wasn't supposed to) and I accidentally ended up inhaling it and felt like I was suffocating for a couple of minutes after that. Great hub! Voted up!

    • LagunaAlkaline profile image


      6 years ago from Camas, WA

      Great hub! I didn't recognize some of these signs. Thanks for writing such a great hub.

    • Jodah profile image

      John Hansen 

      6 years ago from Queensland Australia

      Interesting and helpful hub Susi. I had only seen a few of these signs before, but at least most are self-explanatory. The pictures in most cases reflect the danger well. Thanks for sharing.


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