This article looks at the combustible nature of powdered food substances and how to prevent explosions.
The Danger of Ingredient Dust and Powder
One of the most overlooked aspects of working with ingredients in a food production facility, is the fact that some ingredients have the propensity to cause explosions. These substances include, for example, flour, sugar, dried milk, custard powder, instant coffee and soup powder. Common processes that can create explosive dust in the food industry are flour and provender milling, sugar grinding, spray drying of milk and storage of whole grains. Other processes include using finely sprayed oils, mixing with potable flammable solvents and certain sterilization techniques.
According to the Health and Safety Executive,
“If any combustible substance is mixed or suspended in air at the correct concentrations and contained in a vessel or building when ignition occurs, then a violent explosion can result. If it is uncontained then a fireball may occur.”
On 14th August 2015, a worker at Adams Foods in Leek, Staffordshire, suffered facial burns after a powder explosion. A spokesman for Adams Foods, which supplies ingredients to retailers, said,
“A member of staff working on the production line received minor injuries. Emergency services were called and the incident is now fully under control with all other production lines operating as normal.”
Fortunately, the injured worker was discharged after being treated at the Royal Stoke University Hospital. However, another similar incident could result in far more serious, and even life-threatening injuries. For more information on this story, click here.
For a FREE dust extraction survey of your site, please click here.
What Causes Powder Explosions
Powder explosions are caused by combustible powdered substances in the air, coming into contact with a source of heat.
The Dangerous Substances and Explosive Atmospheres Regulations 2002 (DSEAR) are concerned with preventing or limiting the instance and harmful effects of such explosions.
According to HSE,
“In DSEAR, an explosive atmosphere is defined as a mixture of dangerous substances with air, under atmospheric conditions, in the form of gases, vapours, mist or dust in which, after ignition has occurred, combustion spreads to the entire unburned mixture.”
Considerations When Working with Combustible Powders
In order to operate your process plant safely and to meet DSEAR requirements, you must take the appropriate precautions. These precautions relate to storage and handling, pneumatic conveying systems, chokes etc. To read the recommended precautions, please click here.
Another issue to consider is your ductwork, which can get clogged with extracted dust particles. As well as presenting a significant fire risk, a massive build-up of can dust can even cause ducting to rupture, as a manufacturer of morning foods found recently. Please see our case study for further details.
Download our brochure about HVDS’ dust control services here.
HVDS offers a full dust control solution as per HSG258 and according to COSHH and ATEX regulations.
According to the World Health Organisation (WHO),
“Dusts are solid particles, ranging in size from below 1 µm (micrometre) up to at least 100 µm, which may be or become airborne, depending on the origin, physical characteristics and ambient conditions.”
Dust can be created by manual processes, such as cutting, crushing and grinding and particles can be so small that they are invisible to the naked eye. Different types of dust also carry different risks to human health and can be classified into three types: L Class (Low Risk), M Class (Medium Risk) and H Class (High Risk). Each class has a maximum allowable concentration, which is essential for employers to understand.
L Class Dust (Low Risk)
L Class dust is of lower toxicity and includes simple house dust, soil, general construction dust/waste, soft woods and solid surface material. The workplace exposure limit/maximum allowable concentration (MAC) for L Class dust is >1 mg/m3. This means that you need a dust extractor that catches 99% of the dust. For L Class dust, there should be a Filter Leakage no greater than 1% of the collected dust.
M Class Dust (Medium Risk)
Dusts in the M classification include hard woods (e.g. oak and beech), board material/man-made woods (MDF), repair compound, filler and clear coats, cement, tile cement, brick, mortars (silica), concrete dust, quartziferous materials (e.g. sand) and paints, such as oil paints and latex. They present a medium degree of risk to human health and the workplace exposure limit/maximum allowable concentration (MAC) for M Class dust is ≥ 0.1 mg/m³. Thismeans you need a dust extractor that catches 99.9% of the dust. For M Class dust, there should be a Filter Leakage no greater than 0.1% of the collected dust.
H Class Dust (High Risk)
H Class is high toxicity dusts containing pathogenic or carcinogenic particles, as well as asbestos, mould spores, bitumen, mineral fibres and artificial mineral fibres, like glass wool. They present a high degree of risk to human health and the workplace exposure limit/maximum allowable concentration (MAC) for H Class dust is < 0.1 mg/m³. This means you need a dust extractor that catches 99.995% of the dust. For H Class dust, there should be a Filter Leakage no greater than 0.005% of the collected dust.
Another category of dust, as highlighted by Health & Safety Executive (HSE) is combustible dusts. A combustible substance, mixed with air and with the addition of a source of ignition will cause an explosion. Workplaces that typically produce potentially explosive atmospheres include those handling fine organic dusts, such as wood or flour dust and those where processes release flammable gases or vapours, such as vehicle paint spraying. The Dangerous Substances and Explosive Atmospheres Regulations 2002 (DSEAR) make employers responsible for eliminating or controlling the risks from explosive atmospheres in the workplace. According to HSE,
“In DSEAR, an explosive atmosphere is defined as a mixture of dangerous substances with air, under atmospheric conditions*, in the form of gases, vapours, mist or dust in which, after ignition has occurred, combustion spreads to the entire unburned mixture.”
*Atmospheric conditions are commonly referred to as ambient temperatures (–20°C to 40°C) and pressures (0.8 to 1.1 bar).
There are two European Directives for controlling explosive atmospheres: Directive 99/92/EC (also known as ‘ATEX 137’ or the ‘ATEX Workplace Directive’) and Directive 94/9/EC (also known as ‘ATEX 95’ or ‘the ATEX Equipment Directive’).
Dust Control Considerations
It is important to use the right dust extraction equipment. In fact, HSE are giving out substantial fines where the wrong/no dust extraction equipment is being used.
When choosing dust extraction equipment the following should be taken into account:
- Type of dust you need to control (L, M or H Class, explosive dust)*
- Volume of dust to be extracted to match the extraction rate
- Storage capacity of the extractor
- Disposal of dust – with secure disposal required for H Class waste
* most L and M Class dust extractors will have similar suction rates and filtration levels
Different types of dust present different risks. At HVDS, we help you choose the right dust control solution for your particular workplace. For more information contact us here. To find out more about our dust, fume, mist, spray and oil extraction service, click here.
Local Exhaust Ventilation (LEV) systems control substances hazardous to health and every company providing LEV extraction equipment has a legal requirement to comply with COSHH Regulation 9, in order to protect its employees.
“Proper maintenance is a vital part of any control regime and inspectors and enforcement officers should ensure that employers comply fully with regulation 9, particularly where there is exposure to substances that can cause cancer or asthma.”COSHH Regulation 9 – Maintenance
How An LEV System Works
Many processes create harmful dusts, fumes and vapours that are hazardous to health. LEV systems use extract ventilation to transport these airborne contaminants away from the employee’s breathing zone. Pollutants are drawn away from the process by means of an extraction hood, booth or other device placed over or around the area in which the harmful substance is being released. Ducting to the inlet of a fan is connected to the device so that the extracted air can be discharged to the atmosphere or cleaned and then released.
In order to ensure that your system is in a good state of repair and works efficiently, a thorough examination and testing should be carried out a minimum of every 14 months. In some cases, examinations should be more frequent. If you are unsure how frequently your LEV system needs testing, please contact us here.
Employers must keep a record of LEV examination and testing, including any remedial repairs undertaken as a result of the examination and test, for a period of at least 5 years.
How We Can Help
We provide a comprehensive LEV testing service to ensure your systems are compliant. Our accredited engineers are trained to BOHS standards and will carry out an examination according to COSHH Regulation 9 (HSG258) See the HSE publication, Controlling airborne contaminants at work: A guide to local exhaust ventilation (LEV), for more information.
We also provide Workplace Air Monitoring and will provide a full report of your current Indoor Air Quality (IAQ).
For more information about our dust extraction service, please click here. Alternatively, please contact us on 01785 256976 or at email@example.com Due to continued company expansion, we are currently recruiting for an LEV Testing & Mechanical Service Engineer. For more information about this role, please click here.
At HVDS, we have a very dedicated team of specialists in dust extraction. Their commitment to our customers is second to none. So when they gain their BOHS LEV qualifications and pass their exams with flying colours, we can only feel a sense of great pride in the knowledge that they will be using their new skills to serve our customers even better.
Pictured here are Darren Carvell, our Dust Extraction Specialist, and Jane Boon, our Dust Aftermarket Sales & Contracts Manager. They have both successfully completed the BOHS P600 course (Methods for Testing the Performance of Local Exhaust Ventilation Systems) with only one point off full marks!
A few days prior to this success, our Dust Extraction Manager, Carl Latham, passed his P604 theory exam! This success can be added to Carl’s other LEV qualifications and BOHS accreditations (P601, P602 and W201).
The P604 course (Performance Evaluation and Management of LEV Systems) is for engineers, supervisors, managers, health and safety professionals and technical staff who have day to day dealings with LEV equipment.
Many thanks to Local Exhaust Ventilation (LEV) training provider, OXYL8 Ltd, for helping our team meet the qualification and membership requirements of the Institute of LEV Engineers (ILEVE).
The BOHS is the British Occupational Hygiene Society, which provides information about managing and controlling workplace health risks. A guide to all their LEV quaifications can be found here. The BOHS strives to create a healthy working environment for everyone.
One of our core values here at HVDS is to ‘strive for continuous improvement, in a culture of progress’. Well done to all who have recently qualified and good luck to those still awaiting their exam results.
If you would like to speak to our dust extraction experts about issues affecting your workplace environment, please get in touch here. We offer a FRE dust, fume, mist, spray and oil site survey to help you make informed decisions. Request your survey here. For more information about our dust, fume, mist, spray and oil extraction service, please click here.
In this infographic we take a look at Dust Control Systems, and what you should be checking as part of your regular maintenance schedules.
For a more in-depth look at the following points, click here:
1.) How Dust Control Systems work
2.) Prevention and maintenance of poorly kept systems
3.) How Dust Control can affect employee health and well-being
At HVDS we get a lot of enquiries from customers regarding maintenance and investigation into their current systems. It is during these investigations and surveys that we come across situations like this one.
A customer requested we investigate the reason behind a lack of extraction from their Dust Extract Unit (DEU) in their ingredients blending room.
Here is what we discovered on site.
So, what is wrong with this picture?
Our investigation found that the ductwork was severely contaminated, resulting in the reduction of the DEU’s ability to extract dust.
Solving the problem – how did we proceed?
HVDS carried out a full ductwork system deep clean followed by a DEU filter change. This dramatically improved the hygiene levels by improving the Indoor Air Quality of the ingredients room.
The clean and filter change enabled the dust extractors to begin working to their full capacity once again, resulting in a clean and compliant production environment.
What could have been done to avoid this?
A regular maintenance plan is always advised to avoid situations like this one.
While an engineers time can be limited, with other responsibilities such as production maintenance and management, the time taken to carry out regular checks can be extremely beneficial and incredibly cost effective in the long run.
How can HVDS help you
At HVDS we can offer free ‘behind the scenes’ surveys to give you peace of mind and to ensure that your production environments are compliant and working correctly.
Contact us today on 01785 256976 to find out more about our air filter and extraction solutions.
The HSE have issued the following safety alert:
There is new scientific evidence from the International Agency for Research on Cancer that exposure to mild steel welding fume can cause lung cancer and possibly kidney cancer in humans.
The Workplace Health Expert Committee has endorsed the reclassification of mild steel welding fume as a human carcinogen.
With immediate effect, there is a strengthening of HSE’s enforcement expectation for all welding fume, including mild steel welding; because general ventilation does not achieve the necessary control.
What you need to do:
- Risk assessments should reflect the change in the expected control measures.
- Make sure exposure to any welding fume released is adequately controlled using engineering controls (typically LEV).
- Ensure that suitable controls are provided for all welding activities, irrelevant of duration. This includes welding outdoors.
- Where engineering controls alone cannot control exposure, then adequate and suitable RPE (respiratory protective equipment) should be provided to control risk from any residual fume.
- Ensure that all engineering controls are correctly used, suitably maintained and are subject to thorough examination and test where required.
- Make sure any RPE is subject to an RPE programme. An RPE programme encapsulates all the elements of RPE use you need to ensure that your RPE is effective in protecting the wearer.
How can HVDS help:
Should you have any questions about the impact of this on your business, our LEV technical specialists and engineers are here to assist. Get in touch today on 01785 256 976 or email firstname.lastname@example.org.
The food processing industry, along with other industries such as medical and pharmaceuticals, has the necessity for clean rooms that can monitor particle count, type, and size, and therefore require dust controls systems to remove potentially dangerous particles from the air that can cause an explosion and are also necessary for the breathing safety of employees. In essence, dust control is essential for maintaining workplace safety.
So, how do dust control systems work?
Simply put they work by capturing particles and accumulating them in a collector until safely disposing of them, somewhat like a large and powerful vacuum cleaner.
Fans create a suction that draws the particles suspended in the air to the collector via ductwork. In the collector, the contaminated and clean airs are separated. For example, a system will push the contaminated air into the top of the collector and once inside will force it downward to the bottom. The contaminants hit the sides of the collector and then fall to the bottom while the clean air is pushed out and into another filtration system to collect the finest particles.
Why is dust control so important?
The twin threats in a food processing environment are deflagration (combustion that propagates through a gas) and disease. Both threats are caused by a fine powder of particulates that accumulate in the air within these facilities. The most efficient way to neutralize both risks is to remove these suspended particles from the atmosphere.
Deflagration is an explosion caused by the extremely rapid transfer of heat through the air and factories. Processing plants that allow suspension of particulates to propagate are setting up the environment for such an explosion. In fact, a secondary explosion usually follows, precipitated by the rapid rise in pressure caused by deflagration. As the explosion picks up fuel from the air and spreads, it can become even more destructive than the initial detonation. The entire facility can be levelled, resulting in massive loss of life and material. Dust control removes particles from surfaces and the surrounding atmosphere and significantly minimizes this danger.
In every heat explosion, there are three elements present, known as the “fire triangle”, these are oxygen, heat and fuel. When these elements are present, an explosion occurs. If suspended particulates accumulate in the air, their combined surface-area-to-volume ratio makes them highly combustible and even what may seem to be ordinary, everyday substances can become a risk.
Of course, removing heat sources is very costly and often difficult. The most effective way to minimize the risk of deflagration is to remove the elements of dispersion and fuel from the surrounding environment. This is most easily accomplished through dust control.
So, neglecting dust can have explosive consequences. Substances regularly used in industrial cooking and baking including flour, sugar and various powders, all have the potential to explode.
When substances are finely ground inside baking and cooking appliances they can create a dust cloud. This dust, when suspended and mixed with air, can cause large and even fatal explosions.
Bag tip units and bulk silo venting equipment is sometimes overlooked, but it is vital in the food manufacturing industry. These systems help reduce the amount of dust that is left over, dust that has the potential to cause explosions in the future.
Prevention is better than cure so actions such as: –
- Looking at where equipment is positioned and ensure there are no leakage points around handling systems that produce dust.
- Vacuum clean-up systems can also be used to ensure vessels and equipment are left scrupulously clean.
Let’s also take a look at the health risks for workers in a food processing plant. We know that suspended particles are readily inhaled and so removing powders from surfaces and air will minimize the health risks associated with working in these plants. Although the lungs can expel most powders to some extent, they cannot eliminate them entirely. Over time, these substances collect in the lungs and may result in irreversible health conditions. So once again, dust control is critical for safeguarding employee health.
There is something known as “Farmers lung” which can be caused from particles expelled by grains. Farmer’s lung can cause fibrosis, or scarring, of the lungs. This results in reduced breathing capacity and makes it more likely that cancer and other chronic diseases will develop. While removing a source of heat may help curtail deflagration to a point, it will not eliminate the health risks caused by suspended particles. Only dust control, performed through filters and vacuums, can accomplish this.
Prevention and Maintenance
It goes without saying that neglecting dust can have serious consequences and substances that are commonly found in the food processing industry such as flour, sugar and various powders, all have the potential to explode and so preventative maintenance is vitally important.
What sort of maintenance requirements are needed for dust control systems?
The following maintenance activities need to be carried out:
- The collector and filters must frequently be cleaned to enable the machine to run properly.
- The fan and electrical switches and boxes have to be frequently cleaned.
- The cooling vents of the machinery must be kept clean as well to prevent the machines from overheating.
- There should be an inspection for leaks in the vacuum hoses or ductwork after the cleaning. Leaks make the machine less efficient and can actually spread the contaminated particles rather than collect them.
Employee Health & Wellbeing
Employees are the most valuable asset to any business. As well as a moral obligation to protect a company’s workforce, there is also a legal obligation.
Dust that is produced as a result of food production, can also have serious effects on the health and wellbeing of employees. Exposure to dust can cause serious skin conditions and even occupational asthma, when flour dust is breathed in. In fact, respiratory conditions among bakers are now the highest of any occupation in the country.
The HSE sets a long-term Workplace Exposure Limit of 10 mg/m3 (averaged over 8 hours) and a short-term exposure limit of 30 mg/m3 (averaged over 15 minutes). Breaching of these standards can result in severe penalties, loss of productivity due to employee sickness and even legal action.
Last year, an employee from a baking company in Southampton was awarded a five-figure sum after developing occupational asthma due to over exposure to flour dust. For small or large food manufacturers, looking after employee health by reducing dust exposure is vitally important.
Also, in late 2016, a bakery company in Stevenage was fined over £36,000 for failing to comply with the Health and Safety Executive (HSE) standards — a very real threat to smaller businesses.
The HSE is continuing its proactive assessment of food manufacturers for dust control and issuing penalties for the breaching of standards, but it is not just the threat of being penalised that means it is vital for the industry to take dust control more seriously. It should be about the what that companies go about their business. “This is the way we do things around here”.
A final word on the environment
Whilst most food products by their nature are not hazardous to the environment there is still a legal obligation to comply with emissions according to EPA.
For more information and advice on dust control, air filtration and ventilation contact us at HVDS on 01785 256976 or email@example.com.