Treating exhaust air in commercial kitchens
 
THE MODERN COMMERCIAL KITCHEN
 

 

BENEFITS OF AIR TREATMENT

Our vision of the modern commercial kitchen is a kitchen that has a high level of fire safety, offers a better working environment, does not release odors in the kitchen, within the property nor its surroundings, has lower maintenance costs and above all: the heat in the air from griddles, frying pans, ovens and deep fryers are taken

advantage of. In short: a nicer, safer and more sustainable kitchen. An important step towards a modern kitchen is the efficient treatment of the hot, odorous and greasy kitchen exhaust air. On this page, you will find the knowledge you need in order to achieve that: an efficient treatment of the exhaust air in commercial kitchens.

THE BENEFITS OF TREATMENT
Efficiently and properly treated exhaust air yield many benefits, such as; improved fire safety, optimized heat recovery, odor control, lower operational costs, cheaper duct materail and an environmentally friendly solution.


IMPROVED FIRE SAFETY


OPTIMIZED HEAT RECOVERY

ODOR CONTROL

LOWER OPERATIONAL COSTS

REDUCED ENVIRONMENTAL IMPACT

DUCT MATERIAL

According to an estimate, there are over 13 million restaurants in the world and 25,000 of them are located in Sweden - and this number is increasing rapidly. The majority of all restaurants discharge hot air that is not treated accordingly.

As much as half of the energy consumed by a kitchen establishment dissipates in the form of heat through the exhaust ventilation. Significant energy savings can be made if this heat energy is taken advantage of, instead of released through the ventilation. However, utilizing the heat requires that the exhaust air is properly treated; otherwise, the maintenance of filters, heat exchangers and the channel itself becomes too burdensome and costly.

OZONE TREATMENT
Ozone is a strong oxidant (like chlorine) that effectively breaks down smaller fat particles and gaseous fats in the exhaust air and on the surfaces in the exhaust ventilation. Ozone oxidizes fat to generate water, carbon dioxide and some dust. Ozone treatment allows for continuous purification of the exhaust air when the kitchen ventilation is operating. Ozone is generated on

site by reliable systems that require minimal maintenance. Read more about our solutions and systems here. Efficient and continuous removal of grease and fats in the exhaust air yield many benefits. Fire safety increases considerably, odors are reduced and cleaning of the ventilation ducts is required less frequently, and manual cleaning takes significantly less time. Our ozone systems require low maintenance and supervision, and the return of investment is often as short as two to three years if the heat is recovered properly.

HOW DO YOU CONTRIBUTE TO A COMMERCIAL KITCHEN?
Whether you are a technical consultant who does calculations, drawings and designs for a commercial kitchen, a property owner with an existing commercial kitchen, or planning to incorporate one in the establishment, a property manager who is in charge of the operation of a property with commercial kitchens or a ventilation contractor installing ventilation channels, you will have a huge advantage of the information that we share with you here.

Our sales arguments are based on scientific research and our treatment solutions for exhaust air in commercial kitchens are based on our own research and development for the past 25 years.

Continuously treating the exhaust air year after year have many apparent advantages. Which is most valuable to you? Discover that and much more through Ozone Academy.

 

SIGN UP FOR OZONE ACADEMY - WE SHARE OUR KNOWLEDGE
Ozone Academy hosts courses designed specifically for property owners, technical consultants, ventilation contractors, restaurant owners, duct cleaners and others who want basic knowledge about ozone treatment.

Read more here and sign up today!

ABOVE 40% OF ALL FIRES ORIGINATE FROM A KITCHEN
Three factors are required for a fire to occur; fuel, oxygen (air) and heat. All three factors are present in a hood/exhaust duct filled with greasy highenergy exhaust air generated from e.g. woks, deep fryers and/or griddles. Remove one factor and the fire hazard is reduced.

Approximately 40% of all restaurant and hotel fires originate from the kitchen where about half of the fires start at the stove.

In addition to the risk of injury, the cost of property and material damage is significant, often more than EUR 50000 per restaurant. It also leads to further expenses due to loss of revenue while the restaurant is closed for reparation. The insurance may, or may not, cover this lost revenue.

Liquefied petroleum gas (LPG or LP gas or propane) must be removed at an adjacent fire due to risk of the fire spreading. A fire that starts in adjacent premises threatens to take off if it manages to ignite the grease in a polluted duct.

OZONE TREATMENT OF THE KITCHEN EXHAUST AIR LOWERS THE RISK OF FIRE
Ozone is an efficient tool to chemically decompose grease particles and convert it to carbon dioxide, water and a small amount of dust that is transported through the exhaust duct without adhering to the inner walls. This prevents any accumulation of energy-rich and flammable fat deposits in the ventilation.

COMMON CAUSES OF KITCHEN FIRES

  • Too high temperatures in the deep fryer
  • Highly flammable vegetable oils
  • Old, more flammable oil, in the deep fryer
  • Fat deposits in the flue and ventilation ducts
  • Misaligned sprinklers due to equipment on wheels being moved around
  • Malfunctioning sprinklers due to the fusible links being clogged by grease

IMPROVED FIRE SAFETY
An immediate result of ozone treatment of greasy kitchen exhaust air is that the fire safety is significantly improved. The ozone treatment prevents the formation of fat deposits in the ducts by breaking down the grease whilst airborne. This removes the fuel needed for a fire to start. This also reduces the amount of manual cleaning of the inner parts of the duct and lowers the frequency of replacements of particle filters.

FIRE EXTINGUISHING SYSTEM
The safest way to protect a restaurant from fire hazards in the kitchen and duct is with a fire suppression system over the entire area of cooking equipment and in the kitchen hoods.

Fires involving cooking oils are classified as “Class K” in the United States, and “Class F” in European and Australian systems. The most commonly used agent for K/F class fires is Wet Chemical which is mostly potassium salts mixed with water.
The most reliable systems are based on “saponification”, a process that produces glycerol and fatty acid salt, called “soap”. The reaction is a certain fire extinguisher to fight hot cooking oil and fat fires. The reaction both cools down the oil, removing some of the heat and shuts out the oxygen supply to the fuel. The primary purpose is to protect the kitchen staff and reduce the risk of the fire to spread further.

REGULAR SUPERVISION
Stainless steel ducts are expensive, but also the safest in terms of fire prevention. This is because of the high temperature resistance of stainless steel, which allows it to withstand the high temperatures that occur, for example, during a fire spreading through fat deposits in the ventilation duct. A kitchen exhaust duct with a built-in purification system, such as ozone treatment or UV-lamps, poses a lower risk of fire, which may allow for cheaper materials than stainless steel to be used (depending on your country’s regulations and recommendations regarding fire prevention). Additionally, the need for duct cleaning decreases because grease particles are continuously removed from the exhaust air.

How often the channel needs inspection and cleaning must be decided on a case by case basis.

Contact us if you have any questions.

 

PURIFY THE KITCHEN EXHAUST AIR AND RECYCLE TENS OF THOUSANDS OF EUROS EVERY YEAR!
Greasy and dirty exhaust air is associated with costs. If purified, it would be a valuable resource. A restaurant with about 1 500 m3/h exhaust air loses up to 14 000 euros per year in heat energy depending on the operating conditions. The payback period for an air purification system and a heat recovery unit can be as short as a few years. Kitchen ventilation is needed in order to create a good working environment in the kitchen, to dissipate heat as well as cooking odors and moisture and to supply the area with fresh air. However, in Sweden alone, an estimated 280 million euros disappears in the form of heat energy through the ventilation of our properties. There are ongoing projects designed to make commercial kitchens more energy efficient. Energy savings can be achieved by selecting the right equipment, utilizing demand-controlled ventilation, correct service intervals of the equipment and training of staff. The (heat) energy in the exhaust air from a kitchen constitutes the largest part of the possible energy savings by far – probably as much as 40% of the total energy consumption in a kitchen.

An average sized kitchen can save tens of thousands of euros annually by taking measures that allow heat recovery from the exhaust air with a heat exchanger.

Start purifying the air and installing a heat exchanger. Already at moderate thermal efficiencies, the potential savings are significant.

IN PURELY THEORETICAL TERMS, HOW DO YOU RECOVER THE GREATEST AMOUNT OF ENERGY?
Here are a few tips on how to recover the maximum amount of energy:

1. BUY A HIGH-QUALITY HEAT EXCHANGER
Put time and energy into your choice of heat exchanger. Choose a reliable model with a high efficiency rating, and then make sure to keep it clean to prevent it from losing efficiency. It must be able to work under ideal conditions – at all times. Only then, will you be able to recover the maximum amount of energy year after year.

2. REMOVE AS MUCH GREASE AS POSSIBLE BEFORE THE AIR REACHES THE HEAT EXCHANGER
Make sure the air that reaches the pre-filter of the heat exchanger is as clean as possible at all times. This is important, since large amounts of grease have a number of negative effects. The grease may cause pressure drops in the exhaust duct and the efficiency of the heat exchanger is reduced. Heating costs increase, the pre-filter needs replacing more often and the heat exchanger has to be cleaned more frequently.

3. UNDERSTAND THE ADVANTAGES AND DRAWBACKS OF THE VARIOUS TECHNICAL SOLUTIONS – AND MAKE THE RIGHT DECISION
The hot grease-laden air travels at 3–5 m/s on its way to the heat exchanger. Choose the method that most effectively at removes the billions of small grease particles and aerosols that rush through the air stream. Additionally, choose the solution that manages to keep the exhaust duct clean at all times!

SET HIGH DEMANDS ON THE TREATMENT SOLUTION
The purpose of the treatment solution is to minimize the amount of grease that reaches the heat exchanger. These are the requirements we think should be met by a really good solution:

  • It must remove a high proportion of the grease particles and aerosols in the air stream
  • Any reduction in treatment capacity over time must be no more than marginal
  • The need for service, maintenance and other continuous handling must be minimal
  • The treatment solution must not be the cause of operating outages, pressure drops or generally impact the ventilation as a whole
  • The treatment must be efficient enough to make sure that the exhaust duct rarely requires manual cleaning
  • It must be easy to reduce and increase the treatment capacity

AVOID ACTIVE AND MOVING PARTS IN THE EXHAUST DUCT AND HOOD
We strongly recommend refraining from using any active or moving parts in the exhaust duct and hood. If equipment is positioned in the contaminated air flow, treatment capacity will be reduced quicker, and it will require more cleaning, maintenance and replacement of spare parts.

A highly energy efficient commercial kitchen requires that a combination of factors are properly incorporated.

Studies show that the majority of potential savings can be derived from the five aspects described below, and taking action on these give the highest profit:

  • Technology in the kitchen – choose equipment and tools with low energy consumption and/or demand-controlled operation
  • Ventilation - use demand-controlled ventilation, purify the exhaust air and recover heat from the purified air
  • Cooling: refrigerators, freezer rooms etc. / Replace cooling where possible e.g. garbage rooms
  • Maintenance – regular maintenance of equipment allows their energy efficiency to remain high and constant. This leads to lower energy consumption
  • Staff – educate the staff! The efficiency and use of equipment by the kitchen staff have a large impact on the energy consumption

LESS ODOR PROBLEMS
Cooking fumes contain a large variety of compounds that yield odors (odor molecules). Rancid fat deposits may also contribute to bad odors through the exhaust air that can disturb nearby residents. Bacteria that thrive on fat-based compounds may also emit odorous compounds. The odor compounds from cooking are normally volatile organic compounds (VOCs) that, in contact with ozone, is oxidized to form water, carbon dioxide and some dust.

In addition to increased fire safety and efficient energy recovery, odor reduction is one of the main reasons for using ozone-based air purification.

  • Continuous and reliable purification of air with ozone reduces the emission of cooking fumes considerably. This leads to a reduced risk of complaints from neighbors who may be disturbed by the smell.
  • Requirements for odor reduction are much greater if the exhaust duct is positioned close to residential buildings. In these cases, a complete odor treatment solution should be considered.

If a restaurant business receives complaints about bad odors, the municipality may require that measures are taken in order to be allowed to continue the business. In urban areas, ozone purification of exhaust air may be the difference between obtaining permission or not for running a restaurant business.

RESTAURANT CLOSES DUE TO NEIGHBOR’S ODOR COMPLAINTS
A small complaint from neighbors due to cooking odors can grow to an unmanageable problem. Odor is something highly subjective and complaints from the neighbors due to cooking odors are never good for business. In a worst case scenario, the landlord or authorities become involved inevitably forcing the restaurant to close. However, odors are a difficult field due to the lack of good benchmarks or

instruments for detecting/ measuring it. This means that authorities are often forced to make an assessment based on a subjective perception of smell. A certain smell may be allowed to occur, but it is always on a case-bycase basis depending on the intensity, duration, frequency, time of day and more. If the authorities consider the smell unacceptable they may demand action.

Problems regarding smell won’t go away by themselves as long as the source and conditions remain unchanged. Actions are required and ozone treatment can be used for odor reduction, eliminating or at least limiting the problem. A bureaucratic term may be “interference” or “nuisance”, but we are essentially talking about a bad odor. Firstly, the complaints are addressed to the property owner and/or restaurant owner (they usually have a shared responsibility). If the complaints are ignored, the next instance is usually the authorities.

Therefore, it is important to take a number of factors into account during the design phase:

  • Are there residents in the vicinity of the restaurant?
  • Where is the exhaust air discharged from the kitchen?
  • Type of cooking?

Do not hesitate to ask for our assistance!

NODORA ODOR REMOVAL
Nodora is our in-house developed solution for the treatment of any type of odor problem. Nodora is a perfect complement to our RENA-systemto achieve high-efficiency purification of large and heavily polluted flows.

Nodora is designed to fit most common applications and is therefore of a modular design to enable high efficiency odor removal depending on airflow, the degree of pollution and requirements. In addition,


the product has been designed to operate with minimal pressure drops to broaden the number of application areas without the need for replacing fans or generators. A combination of RENA Kitchen Solutions and Nodora allows for more opportunities during the design phase of a commercial kitchen establishment. Odorous exhaust air can be treated and discharged in sensitive areas such as at ground level close to residential areas.
For more information, learn more about Nodora here or download our brochure.

CASE STUDIES - ODOR REMOVAL
Odors and odor problems are complex and a science in its own right. To remove 50% of the odorous compounds in the kitchen exhaust is rarely representative of 50% removal of the perceived odor.

All odor compounds have their own unique odor threshold (level at which it can be perceived) and odor intensity. With more than 25 years of experience and in-depth research, we are currently able to deliver odor removal solutions that are tailor-made for each project’s own specifications and requirements.

Heat recovery, chemical usage, duct cleaning and general maintenance are all important parameters regarding operational costs in commercial kitchens.

The economy of the property (sometimes even the tenants) gain from utilizing ozone treatment:

  • Optimized heat recovery leads to lower heating costs
  • No usage of chemicals, ozone is produced from ambient air. This means that no frequent purchases, transports, storing, or use of chemicals or bacteria is required.
  • Less duct cleaning, the frequency of mandatory duct cleaning sessions is minimized when the grease is removed before it sticks to any surface.

CLEANING OF THE KITCHEN EXHAUST DUCT
The ventilation system in a kitchen serves to dissipate heat, moisture, grease, cooking fumes and to provide a fresh air supply.

Fat deposits in the exhaust ducts is one of the greatest threats to a commercial kitchen. Grease is flammable, burning at high temperatures and can lead to large, uncontrollable fires that are difficult to extinguish. Consequently, all exhaust ducts in restaurants and commercial kitchens should be regularly cleaned to minimize the fire hazard.

Ozone breaks down grease particles and aerosols in the air on a molecular level. Similarly to how a scissor cuts a fine thread, the ozone “cuts” the organic (carbon) chains in the fat molecules to

generate carbon dioxide, water and some dust. The interior of the exhaust duct and pre-filter can therefore remain clean from fat deposits, which drastically lowers the need for duct cleaning.

The frequency of exhaust duct cleaning is commonly determined by the local municipality and usually regulated by the safety/fire code in order to prevent chimney and kitchen flue fires. The duct cleaning process depends on the layout of the ventilation system. Typically the duct, fan and ventilation unit are sprayed with hot water and grease solvent to remove flammable fat deposits. Apply to one of our free courses through Ozone Academy to learn more about how to lower the operational costs while maximizing the purification of the kitchen exhaust.

A NATURALLY OCCURRING GAS
Ozone is a gas that is naturally present in our environment. It is formed when oxygen, consisting of two oxygen atoms, is subjected to energy from lightning or UV rays. Ozone has a high oxidation potential, which means that it is prone to reacting with other compounds in complete oxidation reactions.

However, ozone is also an unstable molecule, which means that it will spontaneously “revert” into oxygen-molecules if there is no available compound to oxidize. Ozone has a short half-life, especially

when compared to other household cleaning chemicals e.g. sodium hypochlorite that has a half-life of several years depending on the ambient conditions.

Our solutions generate ozone on site using minimal amounts of oxygen from ambient air. This lowers environmental impact compared to other purification methods.

  • No frequent purchases, transports, storing or replenishment of chemicals/bacteria
  • No handling of chemicals
  • The only requirement is electricity

Treating the kitchen exhaust with ozone enables savings such as:

  • Heating costs, up to 80%
  • Duct cleaning, occurs less frequently, which means less downtime for the business
  • Total energy consumption, up to 30%!

Read more about ozone here. If you want to deepen your knowledge about ozone treatment, feel free to apply to one of our free courses through Ozone Academy!

WITH BUILT-IN PURIFICATION, CLASS 2B IS SUFFICIENT
The Swedish regulation for ducts (Imkanal 2012:2) states that if a purification system, such as ozone purification or UV light, is installed in the duct system, a cheaper material can be used for the duct. Any large kitchen powered by electricity or gas classifies as Class 2B and can therefor use black plate or galvanized plate in the ducts instead of stainless steel. Thereby, if the kitchen exhaust is purified with ozone you can save 70-80% of the cost for duct material. The costs vary depending on the length of the duct, number of bends, cleaning hatches and dampers. Using ozone as a purification method reduces grease in the exhaust air and therefor increases the fire safety. However, it is important to have a system that works properly and purifies the exhaust air continuously to maintain a fire safe duct system.

It is always the projector who is responsible for the design, dimensioning and function of the plant. Based on this and in consultation with the client and possibly also the user, the projector should choose the appropriate execution of the duct according to the needs of the business. The projector should consider the nature of the business and what is appropriate to conduct in the premises, and also what possible change in the business in the premises is conceivable. He should also investigate if there are suitable spaces for fan rooms and ventilation installation throughout the building, including exhaust air function. It is also advisable to make choices so that a change of business requires only minor intervention in the ventilation system and in the building. In addition, the projector should find out what type of organization exists around the restaurant business, as some installation components may need continuous and properly

performed maintenance to maintain the intended function.

The following classification provides examples of operations within the five material classes that the industry considers reasonable. They should not be regarded as definitive and do not relinquish the projector’s responsibility.

Class 1A - For all types of cooking
Class 1B - With extinguishing system
Class 2A - For heating kitchens etc.
Class 2B - With built-in purification
Class 3 - Housing, office, etc.

Note that these classifications are specific to Sweden, and your country might have different rules and regulations.