Safety during ultrasonication

James Bond in Casino Royale shoots a propane tank with a handgun. You didn’t miss that did you? If you did, do you at least remember what happens when a gas tank explodes after a crash in Terminator 2: Judgment Day? It’s okay if you don’t, because I’m going to tell  you what happened when the famous ‘rainbow experiment’ went wrong in a lab. Not once but twice.

Chemicals are as nasty as they are shown in films. Chemicals are also very noxious in a chemical laboratory as much as they are at any place else. That’s why wherever you are, whatever you do, chemicals should be handled with care. (Girls, even the acetone that you use to remove nail polish from your nails can catch fire as soon as it comes in touch with an ignition source, i.e. fire.)

Coming to the rainbow experiment. It’s really fascinating to look at. What happens is, when elements such as Na, Sr, K, Li and Cu are mixed with methanol and ignited, they all burn in the colors of a rainbow. You can see its video here.

What went wrong with the rainbow experiment?

A teacher’s chemistry experiment exploded during a demonstration at Beacon High School in Manhattan on Thursday, creating a fireball that burned two 10th graders, one severely, according to Fire Department and school officials. – Chemjobber

It is better to be safe than sorry. As you can see, horrible things have happened, not only to grown-ups but also to children. This doesn’t meant you should avoid doing things that involve risks. Instead, you can do it in a safe way.

As students who had to work in a laboratory, we were told by our professor (Prof. Bhujle) to learn the safety aspects of our respective projects. For those who do not know me or what I was up to during my Masters degree, here’s what I did:

Process intensification using alternative energy source i.e. ultrasound irradiation (sonochemistry), which leads to decrease in energy consumption and waste reduction. Also investigated a Lewis acid catalyzed homogeneous organic condensation reaction and an ultrasound-assisted Pd-catalyzed heterogeneous transfer hydrogenation reaction.

Safety aspects associated with the project:

Ultrasound usage can be categorized as:

  • Low frequency, high power ultrasound (20–100 kHz)
  • High frequency, medium power ultrasound (100 kHz–1 MHz)
  • High frequency, low power ultrasound (1–10 MHz)

The equipment I used to generate ultrasound i.e. ultrasonic bath, runs on a 33 kHz frequency. Hence, it can be taken as low frequency, high power ultrasound.

Contact Exposures:

Contact exposure is exposure for which there is no intervening air gap between the transducer and the tissue. This may be via direct and intimate contact between the transducer and the tissue or it may be mediated by a solid or liquid. Contact exposure can in some cases provide nearly 100% energy transfer to tissue. [1] 33 kHz frequency ultrasonic bath can cause observable effects.

Airborne ultrasound:

The most plausible mechanisms for non-auditory effects of airborne ultrasound on a human are heating and cavitation. [1] An exposure limit for the general public to airborne ultrasound sound pressure levels (SPL) of 70 dB (at 20 kHz), and 100 dB (at 25 kHz and above). [2] The major effects of airborne ultrasound of concern in practice are the result of reception by the ear. To summarize, exposure to ultrasonic radiation, when sufficiently intense, appears to result in a syndrome involving manifestations of nausea, headache, tinnitus, pain, dizziness, and fatigue. The type of symptom and the degree of severity appear to vary depending upon the actual spectrum of the ultrasonic radiation and the individual susceptibility of the exposed persons, particularly their hearing acuity at high frequencies. A concise summary of the physiological effects of ultrasound with specific stated exposure conditions has been given by Acton.

Measures to be taken for safety:

  • Contact exposure to high-power ultrasound must be avoided at all times. [1]
  • Only operators qualified to use the equipment or persons under strict supervision should be allowed within the boundaries of the controlled area while the equipment is operating. [1]
  • Personnel using high-power ultrasound, and safety inspectors in industry should be knowledgeable about the possible harmful effects of ultrasound and necessary protective measures. [1]
  • Warning signs should be placed at the entrance to any area which contains high power ultrasound equipment or applied to each high power ultrasound device. Accompanying each warning sign there should also be a statement indicating the precautionary measures to be taken while the ultrasound power is on. [1]
  • Safety procedures for the protection of personnel are similar to those used for audible noise. The protection for ultrasonic frequencies is expected to be at least 14 dB for ear muffs and rubber ear plugs, and 24 dB for foam ear plugs. [1]

1. Guidelines for the Safe Use of Ultrasound Part II – Industrial & Commercial
Applications – Safety Code 24. Health Canada. ISBN 0-660-13741-0, (1991).
2. AGNIR (2010). Health Effects of Exposure to Ultrasound and Infrasound. Health
Protection Agency, UK, 167–170.

I’ll discuss transfer hydrogenation in subsequent blog posts.

Stay safe. ;)

Safety first with green chemistry

One of the most important parts of doing green chemistry is making the chemistry safe. Doing it safe comes in three parts: Firstly, the products that are made should be safe for the consumers. Secondly, and sadly, the neglected or less seriously taken part, is the safety of those who make these products, at any level of the production line – workers and their neighbors. Thirdly, researchers in a laboratory.

Let’s take an example. Let’s say you are an researcher in a lab, or may be just a college student. What will you do if sulfuric acid spills on the floor? Do you have any idea? Good if you do, but if you don’t here’s what you can do:

  • Put sand on it.
  • Collect it in a tray.
  • Add base: NaOH + H2SO4 = violent. So, we are not going to add NaOH. We’ll have to use another base, that is Na2CO3. Even better if you have CaCO3.

Safety education is very important, you see?

Who makes sure that workers are safe? Legislation and organizations do and every country has its own of doing it. Here’s a list of them:

  1. European Union: European Agency for Safety and Health at Work (Read about REACH here.)
  2. UK: Health and Safety Executive and local authorities (the local council) under theHealth and Safety at Work etc. Act 1974
  3. Denmark: The Danish Working Environment Authority
  4. US: National Institute for Occupational Safety and Health (NIOSH) and the Occupational Safety and Health Administration (OSHA)
  5. Canada: The Canadian Centre for Occupational Health and Safety (CCOHS)
  6. Malaysia: Department of Occupational Safety and Health (DOSH)
  7. People’s republic of China: Ministry of Health is responsible for occupational disease prevention and the State Administration of Work Safety
  8. South Africa: Department of Labour
  9. India: National Safety Council (NSC)

Although the NSC was set up in 1966, Bhopal disaster that occurred in the year 1984 brought even more attention to the importance of safety, not only in India but worldwide. Human loss is also accompanied by monetary loss for the plants involved. “A safe plant is a more profitable plant.”Walt Boyes. One cannot ignore the financial risk that involves with every accident. In financial terms, these risks are known as ‘contingent costs’. Contingent costs include penalties, remediation, personal injury damages etc. Not to mention the damage that is caused to a company as its corporate image and relationships are at risk as well. Take the example of Hindustan Unilever, when its workers were exposed to mercury in the thermometer factory it owned in Kodaikanal. It shut down in 2001.

Now here we are looking at the bigger picture, to keep it all safe. ‘Life Cycle Analysis’ (LCA) gives us that bigger picture. There are softwares out there that can help a company and there are companies which are already at it.

LCA softwares include:

  1. SimaPro
  2. Umberto
  3. GaBi

You will find some more here:

  1. EPA‘s LCA resources

Companies involved in LCA:

  1. Bristol-Myers Squibb
  2. BASF’s Eco-Efficiency Analysis

Inherently Safer Plants – Part II

Volunteer Image Author Meditations

This blog post introduces some common terminologies related to safety, and then moves on to the intricacies of it.

Hazard: A hazard is anything that may cause harm, such as chemicals, electricity, working from ladders, an open drawer, etc.

Risk: The risk is the chance, high or low, that somebody could be harmed by these and other hazards, together with an indication of how serious the harm could be.

Safety engineering: It is an engineering discipline which assures that engineered systems provide acceptable levels of safety.

Hazard Identification Study: It is the process of identifying hazards in order to plan for, avoid, or mitigate their impacts. Hazard identification is an important step in risk assessment and risk management.

Risk assessment: It is the determination of quantitative or qualitative value of risk related to a concrete situation and a recognized threat (also called hazard). A risk assessment is simply a careful examination of what, in your work, could cause harm to people, so that you can weigh up whether you have taken enough precautions or should do more to prevent harm.

Occupational safety and health (OSH): It is a cross-disciplinary area concerned with protecting the safetyhealth and welfare of people engaged in work or employment. The goals of occupational safety and health programs include to foster a safe and healthy work environment.

Hazard analysis: It is used as the first step in a process used to assess risk. The result of a hazard analysis is the identification of different type of hazards.

Now that you know some of the terms that are frequently encountered while approaching this topic, we can move on to the intricacies of it. Before anything, analysis is must, an assessment of a risk. How is it done?

  • Step 1: Identify the hazards
  • Step 2: Decide who might be harmed and how
  • Step 3: Evaluate the risks and decide on precautions
  • Step 4: Record your findings and implement them
  • Step 5: Review your assessment and update if necessary

Follow the link to learn about the five steps to risk assessment.

HAZOP Studies (Hazard and Operability Studies):

HAZOP study is the assessment on adequacy of safety measures taken by industries vis-avis the hazards present and is primarily carried for chemical industries.

Any plant operation sometimes involve deviation from design parameters during the operation. HAZOP study is a structured methodology to identify all possible deviations of the process parameters namely temperature, pressure, composition, direction of flow etc, and all the consequences associated with each deviations. The deviation is also correlated to the safety interlocks, instrumentation and administrative procedure related to the operation.

The output of HAZOP is a list of possible deviations, their causes, consequences, safety measures and additional safety measures required to avoid consequences.


The Occupational Safety and Health Administration (OSHA) has written voluminous occupational safety and health standards and regulations that affect employers and employees in the United States. It is the employer’s legal responsibility to educate employees on all workplace safety standards and the hazards that their employees may face while on the job.

Because different countries take different approaches to ensuring occupational safety and health, areas of occupational safety and health’s needs and focus also vary between countries and regions. Read more here.

Everyone has the Right to Know, the chemicals they are working with, the environment they will be exposed to.

This topic stretches miles. One can go on reading about safety and the laws surrounding it. Last but not the least, we should not forget that we are humans, imperfect, we make mistakes. So, considering this, one also has to study something known as Behavior-based safety. Read more here.

OSH, India:

Before looking at the strategies of making plants safer, lets us first see how it is traditionally done.

LOPA (Layers of protection analysis):

The various measures for prevention and mitigation of major accidents may be thought of as lines of defence’ (LODs) or ‘layers of protection’ (LOPs). These lines or layers serve to either prevent an initiating event (such as loss of cooling or overcharging of a material to a reactor, for example) from developing into an incident (typically a release of a dangerous substance), or to mitigate the consequences of an incident once it occurs. This is illustrated in figure below.

Read more about LOPA, here.

Coming to the strategies, they will be presented in order of reliability:

  • Inherent: Eliminating the hazard by using materials and process conditions which are non-hazardous. It is the most reliable way. How about creating an atmospheric pressure reaction using non-volatile solvents. This way there is no potential for over pressure. Instead of using a corrosive substance like AlCl3 as a regent in huge quantities, we can use catalytic quantities of say, scandium triflate. A scientist, Shu Kobayashi, has researched a lot on Lewis acid catalysts like metal triflates, which are non-corrosive in nature, unlike the usual lewis acid catalysts.
  • Passive: Minimizing the hazard by process equipment features which reduce either the probability or consequence of the hazard without active functioning. Designing a vessel for 4 atm when the operating condition is 1 atm or having equipment before or after the vessel to reduce the excess pressure. A reaction capable of generating 150 psig pressure in case of a runaway, in a vessel designed for 250, this way the reactor can contain the accident unless it is damaged.
  • Active: Using controls, safety interlocks and emergency shutdown systems to detect and correct process deviations (engineering controls). A reaction capable of generating 150 psig in case of a runaway in a 15 psig reactor with a 5 psig interlock that stops feeds and a rupture disk to reduce pressure, directing contents to effluent treatment. What could happen?
  • Procedural: Using operating procedures, administrative checks, emergency response, and other management approaches to prevent incidents, or to minimize the consequences (administrative controls). Consider the same 150 psig reaction, same reactor, without the interlock. The operator is instructed to monitor the pressure and shuts down feed. Mind you, there can be a human error to make it worse, hence it is the least preferred method.

Another way of looking at inherently safer process strategies is this:

  • Minimize: Use of smaller quantities of hazardous substances. (Intensification/Continuous processes)
  • Substitute: Replace a material with a less hazardous substance.
  • Moderate: Use less hazardous conditions, a less hazardous form of a material, or facilities which minimize the impact of a release of hazardous material or energy. (Attenuation or limitation)
  • Simplify: Design facilities which eliminate unnecessary complexity  and make operating errors less likely, and which are forgiving of errors which are made. (Error tolerance)

Do you remember? It is the same strategy we looked up to design safer chemicals.

Further reading:

Last Edited: January 8 2018

Inherently Safer Plants – Part I

Volunteer Image Author DarkSouls1

“What you don’t have, can’t leak!”

These are the words of Mr Trevor Kletz, ICI and LU.

If you develop, operate and control a chemical process such that bad consequences are reduced, owing to different chemistry, chemicals, conditions or simplicity, wouldn’t the safety of the plant be improved? Is this better than layers of protection? Prevention is better than cure.

The inherent safety structure consists of three parts:

  1. Hazard Identification
  2. Hazard Evaluation
  3. Inherent Safety Evolution

A hazard is a physical or chemical characteristic that has the potential for causing harm to people, the environment or property. They are characteristic of the materials, chemistry and process variables.

Let’s see some of the hazards, relating them to their intensity of destruction.

  • Acute toxicity: Chlorine is toxic by inhalation.
  • Chronic toxicity: Sulfuric acid is extremely corrosive to skin. Nuclear material can cause chronic toxicity too.
  • Flammability: Ethylene is flammable.
  • Instability: High pressure confined steam contains a lot of energy.
  • Extreme conditions: Styrene can polymerize releasing heat.

Air pollution, water pollution, ground water pollution, waste disposal are other  examples of consequences.

Representative list of types of hazards:

  1. Fires: Flash fires, Pool fires, Jet fires. For example, ammonia, multi-bond hydrocarbons
  2. Explosions: Vapor cloud explosion (VCE), Confined deflagration, Detonation, Pressure vessel rupture. For example, multi-bond hydrocarbons, epoxides, hydrides and hydrogen, metal acetylides, nitrogen compounds, oxygenated compounds of halogens, oxygenated manganese compounds, peroxides.
  3. Toxicity: Environmentally (chronic, acute, individually toxic, broadly toxic), pesticides, fungicides, herbicides, insecticides, fumigants. For example, ammonia, chlorinated hydrocarbons, cyano compounds, polychlorinated biphenyls, poly-cyclic aromatic hydrocarbons.
  4. Product: Customer injury, waste disposal

Are there other hazards associated with dangerously reactive chemicals?

Many dangerously reactive materials can also undergo dangerous reactions from direct contact with other and incompatible materials. Incompatibility hazards can be complicated. The chance of a dangerous reaction depends not just on the different combinations of chemicals involved, but it also depends on the amounts of each, the surrounding conditions such as temperature, and whether the substances are enclosed in a sealed container or not.

The SDS and the container labels should explain all of the hazards of the dangerously reactive liquids and solids that you work with.

Reactive combinations of chemicals:

  • Acids + chlorates = spontaneous ignition
  • Acids + cyanides = Toxic/flammable gas
  • Acids + fluorides = Toxic gas
  • Acids + epoxides = Heat/Polymerization
  • Alkali + nitro compounds = Easy to ignite
  • Alkali + nitroso compounds = Easy to ignite
  • Ammonium salts of alkali metals + chlorates = Explosive salts
  • Ammonium salts of alkali metals + nitrates = Explosive salts
  • Ammonium salts of alkali metals + alcohols = Flammable gas
  • Ammonium salts of alkali metals + glycols = Flammable gas
  • Ammonium salts of alkali metals + amides = Flammable gas
  • Ammonium salts of alkali metals + amines = Flammable gas
  • Ammonium salts of alkali metals + azo compounds = Flammable gas
  • Ammonium salts of alkali metals + diazo compounds = Flammable gas
  • Inorganic sulfide metals + water = Toxic/Flammable gas
  • Inorganic sulfide metals + explosives = Heat/Explosives
  • Inorganic sulfide metals + Polymerizable compounds = Polymerization

Read more:


Dangerously Reactive Liquids and Solids – Hazards

Last Edited: January 8 2018