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Grain Dust: Characteristics, Composition, and Safe Gas Cleaning

Grain dust is a substance that is formed during production processes related to grain handling and storage. It consists of tiny particles of straw, husks, weed seeds, and grain embryos. The main cause of dust formation is the friction between grains, as well as between grains and the equipment walls. The primary danger of dust from grains is its highly combustible nature.

Grain processing facilities: elevators, mills, cereal processing plants, feed mills, silos, as well as seed production enterprises — are considered high-dust environments.

In this article, we investigated the impact of grain particles on health, causes of explosion and fire, safety measures, properties and characteristics, and most importantly, dust collection and control systems.

Grain Dust Health Effects

Grain dust exposure can pose various health risks and negatively impact respiratory health. When individuals inhale grain dust, especially in large amounts or over prolonged periods, it can cause several adverse effects in the lungs. Allergy symptoms related to air pollution from grains may include respiratory issues, such as coughing, wheezing, and shortness of breath. The dust particles can also irritate the skin, leading to the development of a rash or other allergic reactions. In certain instances, can contain toxins or contaminants that may result in poisoning if ingested or absorbed through the skin. It is important for individuals working in grain-related industries to implement necessary measures precautions to minimize exposure and maintain their respiratory health. Regular use of protective equipment, such as masks and gloves, can help reduce the risks.

Safe Storage of Grain

A grain dust fire is a potential hazard that can occur in industries involved in grain processing and storage. Therefore, it is important to observe safety measures during the storage, transportation, and processing of grain.

The rules for storing grain are regulated by regulatory acts, taking into account the grain dust classification, where it is classified as Class II, Group G.

Based on the research on the causes of explosions and fires in grain processing plants, the main causes of accidents are the lack of:
  1. Explosion protection measures for equipment or their low effectiveness.
  2. Lightweight construction designs in bunkers and silos.
  3. Systems for explosion containment.
Grain Processing
Grain Processing
This is not surprising, as these facilities were often built without considering explosion safety standards, especially in older buildings. However, even in modern large-scale grain processing plants, grain storage facilities, and baking and brewing plants, similar accidents can occur.

Currently, there are two types of technologies aimed at combating grain particles and its spread on the facility's premises. The first option is grain oiling, which helps neutralize the friction effect and reduce the likelihood of suspended particles in the air. However, the more commonly used method is aspiration. The corresponding systems collect air directly from the dust source and purify it using inertial forces or filtration. By employing this method, the dust content in the grain is considerably decreased, thereby minimizing the probability of ignition.

The Purification of Gas from Grain Dust

Dry air cleaning is considered one of the most practical methods. It includes several techniques:
  • Particle settling by gravity — the technique relies on the force of gravity. Under its pressure, particles settle without changing the direction of the airflow.
  • Inertial systems, where suspended particles try to maintain their direction of motion while the gas flow changes.
  • Centrifugal method — it utilizes the appropriate force generated by the rotation of specific equipment parts. Such equipment is called a grain cyclone dust collector.
  • There is also the method of mechanical filtration.
The selection of the cleaning method considers factors such as the dust properties, particle sizes, and facility air temperature, while also accounting for the specific demands of grain dust collection.

Torch-Air Dust Collector
Torch-Air Dust Collector

Grain Dust Collection Systems

The principle of operation of aspiration systems involves extracting dusty air at the source of dust generation and subsequently purifying it using either inertia forces (up to 70%) or filtration elements, achieving a level of air purification of up to 99%. These systems are powered by a fan that draws air from the dust source through the filter and releases it into the atmosphere. Aspiration units can be designed to either remove dust from the production process (used in feed mills, elevators) or return it to the airflow to retain product mass (mainly applied in grain terminals).

Grain dust collection systems are vital for maintaining a safe working environment in grain processing and storage facilities. Several types of systems are commonly used:
  • Cyclone separators: These systems utilize centrifugal force to separate the suspended particles from the air stream. The heavier particles are collected in a container, while the cleaned air is discharged. It consists of sleeve filters of various degrees of purification, as well as a cyclone-type inlet and air cleaning of the filter elements with a fan.
  • Baghouse filters: These systems consist of fabric filter bags that capture suspended particles as the air passes through them. Periodic cleaning of the bags ensures continuous filtration efficiency. It is suitable for operation in highly contaminated conditions for the filtration of dry coarse and fine particulate particles. They have high efficiency and can purify the air from pollutants up to 99.9%.
  • Wet scrubbers: These systems use water or a liquid mist to capture and remove dust particles from the air. The dust-laden air is passed through the scrubbing liquid, which absorbs the particles. Wet dust collectors are primarily used in cases where there is a need to capture large quantities of fine-dispersed particles.
By implementing effective grain dust collectors, facilities can minimize airborne dust levels, reduce the risk of dust explosions, and promote a healthier working environment for employees.

We are a manufacturer of air purification equipment. We design and supply air cleaning systems, including the necessary collectors. Feel free to reach out to us, and we will be glad to assist you!

Grain Cyclones

Grain dust cyclones are considered the most popular and efficient type of aspiration equipment for grain dust. These devices combine inertial and gravitational cleaning methods. The following algorithm is implemented in the systems:
  1. Dust-laden air enters the unit through the inlet located at the top.
  2. The apparatus creates a rotating gas flow downward towards the conical section.
  3. Due to the inertial force, particles exit the flow and settle on the cyclone walls.
  4. They are picked up by a secondary airflow and carried down to a dust collection reservoir.
  5. The purified air exits upwards and is discharged from the apparatus through a special pipe.
Grain cyclones can be straight-through or reverse-flow, and they differ in the sizes of the cylindrical and conical sections. The efficiency of the equipment is determined by the air entry velocity, cyclone diameter, as well as the inlet and outlet ducts.
Cyclone Bag Filter for Grain Dust
Cyclone Bag Filter for Grain Dust

Advantages of cyclone

Grain dust control systems are implemented to effectively manage and reduce the presence of dust.
  • Highly efficient removal of air pollutants.
  • Reliability and long service life.
  • Ease of operation and maintenance.
  • High productivity.
  • Safety due to the absence of moving parts.
  • Wide temperature range of operation.
  • Resistance to high pressure.
  • Stability of hydraulic resistance.
An undeniable advantage is the ability of the equipment to maintain all functions even at high suspended particles concentrations.

Another advantage is the extensive selection of devices based on characteristics and purpose. For example, a grain cyclone separator is used to remove dust from the air. The devices are available in right and left versions with various sizes. Cyclone unloaders for grain are used to separate the conveyed material from the airflow. They also vary in technical parameters.

Grain Dust Suppression

Grain dust suppression systems encompass various methods and practices aimed at reducing or controlling the generation and dispersal of dust. Here are some common techniques used:
  1. Moisture control: Maintaining proper moisture levels in grain storage areas can help reduce the generation of air pollution. This can be achieved through appropriate grain conditioning and storage techniques.
  2. Dust containment: Implementing measures such as enclosing equipment, using dust curtains or shields, and sealing openings can help contain dust within specific areas, preventing its spread.
  3. Dust suppression agents: Applying dust suppressants or surfactants on grain surfaces can help reduce airborne particles formation and make the particles less prone to becoming airborne.
  4. Dust extraction systems: Utilizing local exhaust ventilation systems and dust collectors near dust-emitting processes can effectively capture and remove particles that pollute at the source.
  5. Regular cleaning and maintenance: Regular cleaning of equipment, machinery, and storage areas can prevent dust buildup and minimize the chances of dust becoming airborne.

Probability of Explosion and Ignition

Grain dust is highly flammable and can instantly ignite when exposed to increased temperature or even a small spark. An explosion occurs, and rarely is it a single event. Explosions can propagate in a chain reaction to other areas and even to connected facilities through technological communication channels.

Primary explosions often occur in storage containers such as bunkers and silos. Dust that accumulates in corners is particularly hazardous. The shockwave lifts the suspended particles upward, turning it into fuel for secondary explosions.

During the initial explosion, it is possible to mitigate the pressure build-up by opening windows and doors. However, during secondary and subsequent explosions, the pressure becomes so intense that this method no longer works.

A grain dust explosion involves the instantaneous ignition of particles. In terms of destructive force, it surpasses dynamite and, in enclosed spaces, leads to the generation of excessive pressure that significantly exceeds the structural capacity of reinforced concrete.

According to grain dust explosion statistics, as reported by a source in West Lafayette, Indiana, the United States experienced a total of nine incidents in 2022, demonstrating an increase from the seven incidents reported in 2021. These figures also indicate that the average number of explosions per year over the past decade stands at 7.8. These statistics highlight the ongoing concern and need for preventive measures in the grain industry to mitigate the risks associated with grain dust explosions.

Why does grain dust explode? Agricultural dust can explode under certain conditions due to its combustible nature and the presence of an ignition source. When grain is processed or handled, fine particles of dust are generated and become suspended in the air. If the airborne particle concentration reaches a critical level and encounters an ignition source (sparks, open flames, or electrical equipment), it can cause a dust explosion. That's why grain dust is so explosive.
Note: A particle concentration of 40 g/m3 is considered an indicator of explosive potential.

Let's list the explosive properties of grain dust. Grain particles has a large surface area that enhances its combustibility. This creates a potentially explosive mixture. Oxygen is crucial for combustion, and if the suspended particles concentration reaches a critical level and encounters an ignition source, such as sparks or open flames, it can lead to a rapid and destructive explosion.

Important Indicators of Explosivity


MIE (Minimum Ignition Energy) refers to the lowest amount of energy required to ignite airborne particles. Determining the MIE of grain dust is essential in assessing its potential explosibility and establishing appropriate safety measures.

Below are the MIE values of dust commonly found in grain processing facilities.

The Minimum Explosive Concentration of Grain Dust

The MEC is the minimum dust concentration required for a combustible mixture. It varies for airborne particle based on factors like grain type, moisture content, particle size, and other combustible materials present.
The MEC range for suspended particles is approximately 50-150 grams per cubic meter.

Deflagration Index Kst

The grain dust Kst, also known as the Deflagration Index, has been determined to be 89 bar m/sec based on thorough explosion testing. It indicates the rate at which a dust explosion can propagate once ignited.

Grain Dust Explosion Control

Grain dust explosion prevention is of utmost importance in industries involved in grain processing and storage. Implementing effective preventive measures can significantly reduce the risk of explosions. Regular cleaning and maintenance of equipment and storage facilities help minimize the accumulation of combustible air pollution. Proper ventilation systems ensure the removal of airborne particles, preventing its concentration. Employing explosion-proof electrical systems and equipment reduces the potential sources of sparks or flames. Conducting training programs and promoting awareness among workers about the hazards of grain dust and the importance of safety protocols further contribute to prevention efforts. By prioritizing grain dust explosion prevention, industries can create a safer working environment for their employees.
Grain Dust Explosion at the Elevator
Grain Dust Explosion at the Elevator

Properties of Grain Dust

Grain dust calculation is based on data regarding its quantity in 1 m3 of exhaust air from grain drying equipment. A value of 30-50 mg/m3 is considered acceptable. An alternative calculation can be made based on the concentration of the substance in the working area of the elevator.

The explosiveness is assessed based on the following factors:
  • Concentration: Particles need to be in close proximity for some of them to ignite others, raising their temperature above the ignition point.
  • Particle size: The particle size determines the amount of heat generated by each particle. This value depends on the grain type and dust composition. Smaller particles result in more intense contact and a stronger explosion.
  • Particle composition: Typically, the composition of the particles is identical to the product present in the grain storage facility. However, each particle contains various types of molecules with different combustion heat. The chemical composition of the particles determines the minimum ignition temperature and the energy of ignition.
  • Dust moisture: Moist particles first dissipate energy to increase their temperature and then expend it on converting water into steam and releasing it. Consequently, the higher the moisture content, the lower the risk ignition.
  • Surrounding conditions: Air temperature and humidity play a role. In high ambient temperatures and humidity, the grain moisture content also increases. The vapor enhances heat conduction, improves heat transfer between particles, and increases atmospheric electroconductivity. Under such circumstances, the dissipation of static electricity is accelerated.
Agricultural dust detonation and ignition are possible when several factors are combined, including a mixture with air, sufficient particle concentration, the presence of an ignition source, and a minimum of 8% oxygen.

Understanding what makes grain dust explosion is crucial in ensuring safety in industries involved in grain processing and storage.


Dust poses a significant hazard, and it is crucial to follow proper aspiration and safety protocols. We have expertise in efficient dust collection.

Our company, Torch-Air, specializes in manufacturing filters for air purification, addressing all types of dust and contaminants. We offer free calculations, equipment selection, and expert consultations. With our advanced solutions, we ensure clean and safe air environments. Our team of professionals is dedicated to providing tailored recommendations and assisting you throughout the process. Experience the efficiency and reliability of our filtration systems and breathe easy with Torch-Air. Contact us today for personalized air purification solutions.
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