Odour Exasperation Here is what you can do in your restaurant

Smell or Odour? What is it?

The sense of smell is the principal method by which humans and other animals detect molecules in the air.  Our perception of smell is the result of several complex processes.  The brain must interpret the reaction of specialised receptor cells in the nose to airborne molecules that deposit on their surface.  Rarely do we experience smell due to the presence of a single chemical.  In most cases, our perception of smell results from the combined effect of many different molecules in the air, e.g. the smell of domestic rubbish or cooking odours. Smells can be pleasant or unpleasant. The term odour is normally used to refer to unpleasant smells. Our interpretation of a smell or odour depends on several factors including prior experience, the current location and our expectations for that environment. For example, jasmine or lavender odour at a spa can be soothing and relaxing to many but the odour coming from cooking, restrooms, drains or waste food at or close to a restaurant are likely to be unacceptable.
Some molecules are classified as irritants. In addition to creating an odour nuisance, they have a negative impact on the human body. The classic example is the activation of the tear ducts when chopping onions. In city centres, nitrogen dioxide and ozone are irritant gases that are responsible for respiratory disease. In extreme cases, molecules can be toxic and lead to fatalities at critical concentrations.  All airborne molecules are extremely small and when inhaled, they are easily transported through the respiratory system, pass through the lungs, and are distributed throughout the body, including the critical organs. The control of odours from restaurant kitchens is one of the countless critical applications for molecular filtration.  

A. Finding the source of the odour

• the ingredients used, (onion, garlic, spices)
• type of food being cooked, (hamburger, pizza, steak)
• the cooking method (grilling, BBQ, boiling)

The emissions from a kitchen include a range of particle sizes, from coarse to very fine smoke, oil and grease aerosols and molecular pollutants. The molecular pollutants are mostly responsible for odour.  However, very fine particles and aerosols can also trigger an odour response if they reach the receptor cells in the nasal passages. There is a recognised method called Olfactometry, implemented as a European Standard (EN13725) for measuring the characteristics and strength of a smell or odour.

B. Using an effective odour control solution

To eliminate 'the stink' in the indoor air, an effective kitchen exhaust filtration system based upon molecular filtration is the key. The kitchen ventilation system should be designed to prevent condensing atmospheres in the exhaust duct, upstream of the filters. 

Particle filtration has two purposes – removing fine particles that can trigger odour response, and protecting the molecular filter.

Molecular filtration uses microporous activated carbon. This media has a large internal-surface to volume ratio and is highly adsorptive, perfect for removing odour molecules from indoor air. Restaurant odours are extremely varied and it is complex to identify the different molecules responsible for the odour. Activated carbon is a broad-spectrum adsorbent and can be used with confidence, without the need for expensive air analysis.

For the relatively small number of molecules that cannot be controlled using broad spectrum media, there are surface-modified or "impregnated" carbons that are intended to specifically adsorb an individual molecule or family of molecules. Activated carbon can be made from different raw materials, in different qualities, shapes, and sizes that can target a wide range of odours, irritants and toxic gases, such as volatile organic compounds (VOC), nitrogen dioxide or ozone. There are very many commercially available adsorbents, they are typically made from activated carbon or activated alumina. Everyone will behave differently towards each of the different molecules in the air. A successful molecular filtration solution will always be fundamentally dependent on the selection of the most appropriate adsorbent. The expert staff in the Camfil molecular filtration test laboratory ensure correct selections are always made.  

C. Maintaining the filtration system and hygiene level

Many restaurants who want to reopen after a halt or temporary shutdown should follow the following steps,

a) If the pre-filters had been installed for a significant period before lockdown (such as 1 month or more), then replace all pre-filters. With organic food particles and grease contamination, they will be likely breeding grounds for microorganisms such as bacteria, mould, fungus.

b) Ensure to physically inspect the molecular filters and if they appear clean and normal, then continue to use. If they are contaminated in any way, a replacement is a must.  

The efficiency of a molecular filter for odour control application can be measured using olfactometry according to EN13725. There are experts at Camfil, who can validate the performance of these solutions with the cooperation of external consultants proficient in this area.