Air Compressor: Types, Uses, and Maintenance

Air Compressor: Types, Uses, and Maintenance

Understanding air compressor involves exploring their types, uses, maintenance, and the various factors to consider when choosing the right compressor for specific needs.

What is an Air Compressor?

An air compressor is a device that converts power into potential energy stored in pressurized air. Essentially, it works by forcing air into a container and pressurizing it. The compressed air is then held in the tank until needed, at which point it is released in a controlled manner to power various tools and applications.

Here’s a basic overview of how an air compressor works and its components:

  • Power Source: Air compressors are typically powered by electricity or gas. The power source drives a motor that compresses air.
  • Compression Mechanism: Depending on the type of compressor, this mechanism could be a piston, rotary screw, or centrifugal impeller. The air is drawn in and compressed, increasing its pressure.
  • Storage Tank: Once the air is compressed, it’s stored in a tank. This storage allows for a steady supply of compressed air that can be used as needed.
  • Control Systems: These systems regulate the pressure by starting and stopping the compressor at preset levels.
  • Output: Compressed air is released through an outlet valve and is used to power pneumatic tools or other applications.

Compressed air is a versatile energy source and is often referred to as the fourth utility in industrial settings, alongside water, electricity, and natural gas. Air compressors are widely used in various industries and applications, including manufacturing, automotive, construction, and more. They power tools like drills, hammers, and sandblasters, and are also used in processes like painting and surface cleaning.

An air compressor is an essential tool in many industries, known for its versatility and efficiency in converting power into usable compressed air for a variety of applications.

What is an air compressor used for?

Air compressors are versatile tools used in various industries and applications due to their ability to provide a powerful and reliable source of energy. Here are some of the primary uses of air compressors:

  • Powering Pneumatic Tools: Air compressors are essential in powering a wide range of pneumatic tools such as drills, nail guns, sanders, and impact wrenches. These tools are commonly used in construction, automotive repair, and manufacturing.
  • Spray Painting: They are used to operate spray guns for painting in automotive workshops, furniture manufacturing, and other industrial painting applications. The compressed air ensures a consistent and even application of paint.
  • Inflating Tires: Air compressors are commonly used in automotive garages and repair shops for inflating tires of vehicles, bicycles, and other inflatable items.
  • Industrial Applications: In manufacturing and industrial settings, air compressors drive machinery and are used in processes such as pneumatic conveying and product finishing.
  • Energy Sector: They are used in the energy industry, particularly in oil and gas operations, for powering tools and equipment.
  • Healthcare and Pharmaceuticals: Compressed air is used in medical and dental equipment, and in pharmaceutical manufacturing, where clean, controlled air is required.
  • Food and Beverage Processing: In the food and beverage industry, air compressors are used for packaging, product handling, and processing operations.
  • Agricultural Applications: They are utilized in agriculture for tasks like operating dairy machines, spraying crops, and ventilating silos.
  • Home and DIY Projects: At home, air compressors are handy for various DIY projects, inflating sports equipment, and small-scale painting jobs.

These varied applications highlight the crucial role of air compressors as a source of power and their adaptability across different sectors. Their efficiency and reliability make them indispensable tools in both professional and personal settings.

Types of Air Compressors

Air compressors are categorized into different types based on their operation mechanism:

  • Piston Compressors: These are common and used for tasks ranging from inflating tires to powering heavy-duty tools. They can be single-stage for lighter tasks or two-stage for high-pressure demands​​.
  • Rotary Screw Compressors: Known for their efficiency and continuous operation, these are used in applications requiring smooth, continuous airflow​​.
  • Centrifugal Compressors: Ideal for large-scale industrial applications, these compressors use high-speed impellers to compress air​​​​.
  • Scroll Compressors: Preferred in environments where low noise is essential, like dental offices or small workshops​​.
  • Rotary Lobe Compressors: Classified more as blowers, they are high-volume, low-pressure devices used in specific industrial settings​​.
  • Axial Compressors: These are used for extremely high volumes of air delivery, commonly found in industrial machines and jet engines​​.

Uses and Benefits of Air Compressors

Air compressors have diverse applications across various industries:

  • Powering Pneumatic Tools: They are used for drills, nail guns, impact wrenches, and more​​.
  • Inflating Tires: Useful in automotive and bicycle shops​​.
  • Spray Painting: Compressed air is essential for powering spray guns​​.
  • Industrial Applications: They play a crucial role in manufacturing and production processes​​.

Benefits of air compressors include versatility, efficiency, cost-effectiveness, consistent supply, and being environmentally friendly​​.

Maintenance and Performance Aspects

  • Compressed Air Receivers: These enhance reliability, increase capacity, improve moisture separation, and reduce noise​​.
  • Optimizing Air Flow: Proper pipe sizing and layout design are crucial for efficient distribution of compressed air​​.
  • Identifying and Fixing Leaks: Regular inspection and maintenance are important for energy efficiency and system longevity​​.

Selecting the Right Air Compressor

When choosing an air compressor, consider:

  • Oil-Free vs. Oil-Injected Compressors: Oil-free models are suitable for environments requiring high-quality air, like pharmaceuticals or food production. Oil-injected models are less expensive and suitable for general manufacturing​​.
  • Piston vs. Rotary Screw Compressors: Piston compressors are less costly and easier to maintain, ideal for environments needing large amounts of air intermittently. Rotary screw compressors are suited for continuous operation and produce less heat​​​​.
  • Power and Fuel Options: Air compressors can be electrically powered or operate on combustible fuels like gasoline or diesel, with electric models being preferred for environments where exhaust fumes are a concern​​.

Air compressors are versatile tools with a wide range of applications in industrial, commercial, and domestic settings. Understanding their types, uses, maintenance requirements, and how to choose the right one can greatly benefit various operational needs. Regular maintenance and proper selection based on specific requirements are key to maximizing their efficiency and longevity.

Applications of Air Compressors

Air compressors are incredibly versatile tools used across a wide range of applications in various industries. Their primary function is to convert power into potential energy stored in pressurized air, which can then be used for various tasks. Here are some of the most common applications of air compressors:

  • Industrial Manufacturing: In manufacturing plants, air compressors power machinery and tools. They are used in assembly lines, production processes, and for pneumatic conveying​​.
  • Automotive Industry: Air compressors are essential in the automotive industry for tasks such as spray painting, operating pneumatic tools, and inflating tires. They are also used in the manufacturing process of vehicles​​.
  • Construction: In construction sites, air compressors power a range of tools such as jackhammers, compactors, and drills. Their portability makes them particularly useful in locations where electric power is unavailable or unreliable​​.
  • Energy Sector: They are used in the energy industry, particularly in oil and gas exploration and production, for powering pneumatic controls and machinery.
  • Healthcare: In hospitals and dental clinics, air compressors are used to power various medical devices and tools, providing a clean and controlled source of air.
  • Pharmaceuticals: In the pharmaceutical industry, air compressors are used in manufacturing processes, particularly where clean and controlled air is required.
  • Food and Beverage Industry: Compressed air is used for packaging, conveying, and mixing products. It’s important in this industry that the air is clean and free from contaminants.
  • Agriculture: Used for powering dairy machines, spraying crops, and operating pneumatic tools for maintenance and repair tasks.
  • Painting and Decorating: Compressors power spray guns for painting cars, furniture, and other items. The compressed air ensures a smooth and even application of paint​​.
  • Home and DIY Projects: For home use, air compressors can inflate tires, operate airbrushes, and drive small pneumatic tools for DIY projects​​.

These applications highlight the importance of air compressors in various sectors. Their ability to provide a powerful and reliable source of energy makes them indispensable in many industrial, commercial, and personal applications.

Choosing the Right Air Compressor

Choosing the right air compressor for your needs involves considering several factors to ensure you get a model that suits your specific requirements. Here are the key considerations:

Type of Compressor:

  • Piston Compressors: Ideal for intermittent use and less costly. Good for environments like garages where compressed air is needed part of the time​​.
  • Rotary Screw Compressors: Best for continuous operation. They are quieter and more efficient for constant use, such as in manufacturing settings​​​​.
  • Centrifugal Compressors: Suitable for large-scale industrial applications needing large amounts of air​​.
  • Other Types: Consider scroll or rotary lobe compressors for specialized applications​​​​.
  • Required Air Pressure and Volume: Determine the necessary air pressure (PSI) and volume (CFM) for your specific applications. This ensures your compressor can handle the tasks you need it for​​.

Power Source and Energy Efficiency:

  • Electric or Gas-Powered: Electric models are preferred for indoor use or where exhaust fumes are a concern. Gas-powered models offer more mobility​​.
  • Voltage Requirements: Consider the electrical supply in your location – whether 120V, 220V, or higher.
  • Portability and Size: If you need to move your compressor between locations, consider the size, weight, and whether it has features like wheels or handles​​.

Oil-Free vs. Oil-Injected Compressors:

  • Oil-Free: Better for environments requiring high-quality air, such as food production or healthcare​​.
  • Oil-Injected: Less expensive, suitable for general manufacturing​​.
  • Noise Level: Consider the operating environment. In noise-sensitive areas, choose models designed to operate quietly​​.
  • Maintenance Needs: Assess the maintenance requirements and ease of service. Piston compressors typically require more frequent maintenance than rotary screw compressors​​​​.
  • Budget and Cost-Effectiveness: Balance the initial cost with long-term operational costs, such as energy consumption and maintenance.
  • Application-Specific Features: Depending on your application, you might need additional features like moisture separators, air dryers, or specific control systems.

By carefully considering these factors, you can select an air compressor that meets your specific needs, offers reliable performance, and provides long-term value. It’s also advisable to consult with a specialist or manufacturer for personalized advice based on your specific requirements and use cases.

Operating and Safety

Operating and ensuring safety when using air compressors involve a set of guidelines and practices designed to ensure efficient operation and prevent accidents or injuries. Here are some key aspects to consider:

Operating Air Compressors

  • Read the Manual: Before using an air compressor, it’s crucial to read and understand the manufacturer’s manual. This provides specific instructions for your model.
  • Regular Inspections: Conduct pre-use inspections to check for any leaks, damaged parts, or loose connections.
  • Correct Settings: Ensure that the pressure settings are correct for the tool or application you are using.
  • Proper Connections: Attach tools and hoses securely. Make sure all fittings and connections are tight to prevent leaks.
  • Avoid Overloading: Do not exceed the compressor’s maximum pressure capacity as this can cause equipment failure or damage.
  • Ventilation: Operate the compressor in a well-ventilated area to avoid overheating and to disperse any emitted fumes, especially if it’s gas-powered.
  • Drain Tanks Regularly: Moisture can accumulate in the compressor tank, leading to rust and decreased efficiency. Drain the tank after each use.
  • Shut Down Properly: Turn off the compressor when not in use and release any trapped air pressure.

Safety Precautions

  • Wear Protective Gear: Use safety glasses, hearing protection, and gloves as necessary.
  • Avoid Direct Air Stream: Never point compressed air at yourself or others. The high-pressure air can cause serious injuries.
  • Check for Hot Surfaces: Parts of the compressor can become very hot during operation. Be cautious when touching the compressor after use.
  • Electrical Safety: If your compressor is electric, ensure it’s connected to a properly grounded outlet. Avoid using in wet or damp conditions.
  • Secure the Compressor: If portable, ensure the compressor is stable and secure during operation to prevent tipping or vibration-related movement.
  • Beware of Gas Emissions: For gas-powered compressors, be aware of carbon monoxide emissions. Use them outdoors or in well-ventilated areas.
  • Train Users: Anyone using the compressor should be properly trained on its operation and safety protocols.
  • Regular Maintenance: Follow a regular maintenance schedule as recommended by the manufacturer to keep the compressor in safe working condition.
  • Emergency Procedures: Have clear procedures in place for handling emergencies or malfunctions.

By following these operating and safety guidelines, you can ensure that your air compressor works efficiently and minimize the risk of accidents or damage. It’s always important to refer to the specific guidelines provided by your compressor’s manufacturer, as different models may have unique features or requirements.

Innovations and Future Trends

The air compressor industry is witnessing several exciting innovations and trends that are shaping its future. These advancements are not only enhancing the performance and efficiency of air compressors but also aligning them with contemporary environmental and sustainability goals.

  1. Portable Air Compressors

Advancements in technology have led to the development of smaller, more portable air compressors. These devices are adaptable for various uses such as construction sites, workshops, remote locations, or emergencies, providing flexibility and enhancing productivity. For instance, Atlas Copco’s X-AIR 850-290 mobile portable compressor is a notable example of this innovation, offering mobility, efficiency, and reduced downtime for construction projects​​.

  1. Eco-Friendly and Oil-Free Air Compressors

The shift towards sustainability has given rise to eco-friendly and quieter air compressors. These compressors are designed to reduce carbon emissions and noise levels, thus adhering to green practices and creating safer work environments. Additionally, the adoption of oil-free air compressors is increasing. These compressors offer cleaner and more reliable compressed air, are better for the environment, and meet stringent quality and regulatory requirements, especially in industries like food and pharmaceuticals​​.

  1. Advanced Technologies and IoT Integration

Air compressors are becoming smarter with the integration of digital controls, wireless monitoring, and data analysis. The use of artificial intelligence, the internet of things (IoT), and predictive maintenance technologies enables air compressors to be more efficient, reliable, and responsive. Predictive maintenance, in particular, uses machine learning algorithms to anticipate potential issues and schedule maintenance proactively, while IoT allows for remote monitoring and control, optimizing performance and reducing energy consumption​​​​​​.

  1. Energy Efficiency and Heat Recovery

The focus on energy efficiency is a significant trend in air compressor technology. Modern compressors are using advanced technologies to reduce energy consumption. For example, the Ultima compressor offers better heat recovery than standard models by using a closed-loop water-cooling system, which not only enhances efficiency but also turns the compressor into a high-efficiency water heater​​.

  1. Industry Trends and Rotary-type Compressors

Rotary-type industrial air compressors are gaining momentum due to their energy efficiency, cost-effectiveness, low maintenance, and versatility. These compressors are well-suited for applications requiring constant, uninterrupted air flow. The market for these compressors is expected to grow significantly, with new models being introduced that offer enhanced efficiency and compact design​​.

  1. Rental vs. Purchase Debate

The decision between renting and purchasing air compressors is becoming a critical consideration for many businesses. Plant managers often weigh the cost-benefit of renting vs. buying based on the duration and frequency of use. If the equipment is required for at least 60-70% of the project lifecycle, purchasing may be more economical​​.

The air compressor industry is evolving rapidly with a strong emphasis on portability, eco-friendliness, technological advancements, energy efficiency, and sustainability. These innovations are not only improving the performance and reliability of air compressors but also reducing their environmental impact, paving the way for a more sustainable future in industrial operations.

Description of Size, Power and weight

The size, power, and weight of air compressors can vary significantly based on their type and intended use. Here’s a general overview:


  • Portable Air Compressors: These are smaller and designed for easy transportation, often used in home projects, small workshops, and on construction sites. Their size can range from small, handheld units to larger models mounted on wheels.
  • Stationary Air Compressors: These are larger and intended for permanent installation in a workshop, factory, or plant. They can be quite large, often requiring a dedicated space.


  • Horsepower (HP): The power of air compressors is measured in horsepower, ranging from as little as 1 HP for small, personal use models to 100 HP or more for industrial models.
  • Pressure: Compressors are also rated by the maximum pressure they can deliver, typically measured in pounds per square inch (PSI). Small models might offer around 90-150 PSI, while industrial models can exceed 1000 PSI.
  • Air Flow: Measured in cubic feet per minute (CFM), this indicates how much air the compressor can produce. Smaller units might offer 1-5 CFM, while larger industrial models can provide hundreds of CFM.


  • Portable Models: These can weigh anywhere from 20 to 100 pounds, designed to be lightweight enough for easy transport.
  • Stationary Models: These can be quite heavy, often weighing several hundred pounds or more, depending on their size and capacity.


  • Small Home Use Compressor: Might be a 1-2 HP model, with a 2-6 gallon tank, delivering around 90-150 PSI and 1-5 CFM, weighing about 20-30 pounds.
  • Professional Grade Portable Compressor: Could be a 4-6 HP model, with a 10-20 gallon tank, delivering up to 200 PSI and 5-10 CFM, weighing around 50-100 pounds.
  • Stationary Industrial Compressor: Might offer 20-100+ HP, with large storage tanks (over 60 gallons), capable of delivering high PSI (over 1000) and high CFM (100+), and weighing several hundred pounds.

These specifications can vary greatly based on the specific model and manufacturer. It’s important to choose a compressor that matches the specific needs of your application, considering the balance between portability, power, and capacity.

A Chart table for air compressor

Creating a chart or table to categorize various types of air compressors can be quite useful for comparison. Here’s a simplified overview:

Type Typical Horsepower (HP) Pressure (PSI) Air Flow (CFM) Tank Size (Gallons) Weight (Pounds) Use Case
Small Home Use 1-2 HP 90-150 PSI 1-5 CFM 2-6 Gallons 20-30 lbs DIY Projects, Home Use
Professional Grade Portable 4-6 HP Up to 200 PSI 5-10 CFM 10-20 Gallons 50-100 lbs Construction Sites, Workshops
Stationary Industrial 20-100+ HP Over 1000 PSI 100+ CFM Over 60 Gallons Several Hundred lbs Industrial Manufacturing, Large Workshops

Please note:

Horsepower (HP): Indicates the power of the compressor’s motor.

Pressure (PSI): The maximum air pressure generated.

Air Flow (CFM): Cubic feet per minute, indicating the volume of air produced.

Tank Size: The size of the storage tank in gallons.

Weight: The approximate weight of the compressor.

This table provides a general overview and typical values for different types of air compressors. Specific models may vary based on the manufacturer and additional features. When choosing an air compressor, it’s important to consider the specific requirements of your application, including the necessary power, size, portability, and capacity.

List of worldwide Top 15 air compressor manufacturing Companies including Web Address

The list of top 15 air compressor manufacturing companies worldwide showcases a diverse range of organizations known for their innovation, quality, and global reach. Here’s a summary of some of the leading companies in this field:

Atlas Copco: Established in 1873, Atlas Copco is a Swedish company renowned for its high-quality compressors, including industrial, dental, and workshop compressors. It operates in over 180 countries and is one of the largest industrial air compressor manufacturers in the world​​​.


General Electric (GE): Founded in 1892, GE is a major player in the global industrial air compressors market. Based in Fairfield, Connecticut, USA, GE’s compressors are utilized in various applications, including petrochemicals and refineries​​​.


Ingersoll Rand: With its origins dating back to 1871, Ingersoll Rand offers a wide range of compressors, including reciprocating, rotary screw, centrifugal, oil-free rotary screw, and oil-flooded rotary compressors. They are known for their quality across small homes to large industrial compressors​​​.


Siemens: Established in 1847 and headquartered in Munich, Germany, Siemens produces turbo and reciprocating compressors primarily for the oil and gas industry and other process industries​​​.


Sulzer: This Swiss company, established in 1834, is a leader in markets like oil and gas, power, and water industries. They produce various industrial compressors, including HST turbocompressors and XTA & XTAK submersible aerators​​​.


BOGE KOMPRESSOREN: A German company founded in 1907, BOGE manufactures a range of products including turbo, piston, scroll, and oil-free compressors, along with compressed air accessories and custom solutions​​​.


Doosan: Based in South Korea and established in 1896, Doosan specializes in compressors ranging from 185 CFM to 1600 CFM, known for models like the XHP750WCU-T4F and XHP1170​​​.


Fusheng: Headquartered in Taiwan and operating since 1953, Fusheng is one of the largest producers of air compressors in China, offering a variety of models including portable, oil-lubricated, and oil-free compressors​​​​​.


Gardner Denver: With its roots tracing back to 1859 in the USA, Gardner Denver offers a diverse range of industrial air compressors for various applications. Their product line includes rotary screw compressors, oil-free compressors, and air treatment products​​​.


Hanbell: Established in 1994 and headquartered in Taiwan, Hanbell manufactures both screw and centrifugal compressors. They have gained recognition for their quality and innovation in the compressor industry​​​.


Sullair: A company known for its commitment to environmental sustainability, Sullair has gained recognition for its advanced air compressor technologies and solutions​.


Kaeser Compressors Inc.: A German manufacturer, Kaeser is renowned for its high-quality products, including the Sigma Air Manager (SAM) system for optimizing compressed air systems​.


CompAir: A subsidiary of Gardner Denver, CompAir is a UK-based leading provider of compressed air and gas systems, known for its wide range of equipment options including micro oil screw air compressors and oil-free screw air compressors​.


ELGi: Headquartered in India, ELGi is a global player in the air compressor market, known for its innovative and high-quality compressed air solutions. They offer a comprehensive range of products catering to various industries​.


California Air Tools: An American company specializing in oil-free, quiet air compressors used in various applications from home use to professional settings​.


These companies represent the forefront of air compressor technology, providing a wide range of products and services globally. Each company brings its unique strengths and innovations, catering to a diverse array of industrial and commercial needs.

Air Compressor: Types, Uses, and Maintenance
Air Compressor: Types, Uses, and Maintenance


The air compressor industry is characterized by a diverse range of products and applications, driven by numerous global manufacturers known for their quality, innovation, and technological advancements. Companies like Atlas Copco, General Electric, Ingersoll Rand, Siemens, Sulzer, BOGE KOMPRESSOREN, Doosan, Fusheng, Gardner Denver, Hanbell, Sullair, Kaeser Compressors Inc., CompAir, ELGi, and California Air Tools, stand out as leaders in the field, each offering unique products tailored to various industrial and commercial needs​​​​​.

These manufacturers are spread across the globe, with headquarters in diverse locations such as Sweden, the United States, Ireland, Germany, Switzerland, South Korea, Taiwan, the United Kingdom, and India. Their products range from small, portable units for home use to large, industrial compressors for manufacturing and other heavy-duty applications. The industry’s focus on innovation, sustainability, and efficiency is evident in the ongoing development of advanced technologies, including oil-free and eco-friendly compressors, smart and IoT-integrated systems, and energy-efficient designs.

The air compressor market is poised to continue its growth and evolution, adapting to meet the increasing demands for energy efficiency, environmental sustainability, and technological integration. As such, these companies are not only contributing significantly to the global economy but also playing a vital role in shaping the future of industrial and commercial operations worldwide.


Here are the references including web addresses for the information provided about the top air compressor manufacturers:

Atlas Copco, General Electric, Ingersoll Rand, Siemens, Sulzer, BOGE KOMPRESSOREN, Doosan, Fusheng, Gardner Denver, Hanbell:

Source: Construction Review Online

Sullair, Kaeser Compressors Inc., CompAir, ELGi, California Air Tools:

Source: Tools Zone

These sources offer detailed insights into the companies mentioned, including their histories, product offerings, and innovations in the field of air compressors. For more in-depth information about each company and their range of products, you can visit their respective official websites.

Frequently Asked Questions (FAQs) about air compressor

Here are some frequently asked questions (FAQs) about air compressors along with their answers:

What are the different types of air compressors?

There are primarily three types of air compressors: reciprocating (piston type), rotary screw, and centrifugal compressors. Each type has its unique mechanism and suitable applications.

How do I choose the right size air compressor?

The size of the air compressor you need depends on the tools you will be using and their CFM (cubic feet per minute) and PSI (pounds per square inch) requirements. Calculate the total CFM required by all your tools and add a margin for safety and future expansion.

What is the difference between an oil-lubricated and an oil-free air compressor?

Oil-lubricated air compressors use oil for cooling and lubrication, which generally makes them quieter and more durable. Oil-free compressors, on the other hand, do not use oil and are lighter and less expensive but may have a shorter lifespan.

How often should an air compressor be serviced?

The frequency of service depends on the type of compressor and usage intensity. Generally, it’s advisable to follow the manufacturer’s guidelines for maintenance schedules.

Can air compressors be used for painting?

Yes, air compressors are commonly used for spray painting. However, it’s crucial to ensure the compressor can deliver the consistent air flow and pressure required by the spray gun.

What safety precautions should be taken when using an air compressor?

Always read the manufacturer’s manual before use, wear appropriate safety gear, regularly inspect and maintain your equipment, ensure proper ventilation, and never exceed the recommended pressure limits.

Why is my air compressor making a loud noise?

Loud noise can be due to several reasons like loose parts, worn-out bearings, improper lubrication, or internal damage. It’s best to consult the manual or a professional for specific diagnostics and repair.

How can I reduce moisture in my air compressor system?

You can use air dryers, drain the tanks regularly, and ensure your system is properly sized and configured to minimize moisture.

What does CFM mean in air compressors?

CFM stands for Cubic Feet per Minute. It’s a measure of the volume of air an air compressor can produce at a given pressure level.

Can I use a generator to power my air compressor?

Yes, but ensure the generator’s power output is sufficient for the compressor’s power requirements.

Remember, it’s always crucial to refer to the specific guidelines provided by your air compressor’s manufacturer for accurate information and best practices.










Leave a Reply

Your email address will not be published. Required fields are marked *