21 October 2016

Odour Control for Hotel Back of House Areas

Hotel back of house areas may be a common source of offensive odours and odour complaints. These areas may include garbage / refuse rooms, loading docks, commercial kitchens, designated outdoor smoking areas or sewer vents.

This article seeks to discuss possible odour control considerations for these back of house areas.

The Science of Odours

Generally, an odour is perceived when chemicals in gaseous form stimulate the receptors in your nose. These odours can be organic or inorganic based. Examples of different, hazardous or unpleasant odours include diesel exhaust, decaying plant matter, sewer gases and mould or yeast spoors due to dampness. Given that the human nose has hundreds of receptors that are uniquely coded by DNA to each individual, reactions to odours can be quite subjective and dependent on individual sensitivities.  An odour that may be pleasant to one – may be unpleasant to another. Similarly the strength of odour perceived from one person to another varies widely, making it difficult at times to achieve an objective assessment.

According to the EPA (the statutory authority responsible for administering the Environmental Protection Act), “an offensive odour is one that affects the general life, health and wellbeing of an individual as a result of the intensity, character, frequency and duration of the odour.” Odorous gases most commonly become an issue because of their nuisance value and – generating complaints by surrounding neighbours. The EPA usually investigates odour complaints for industrial and large commercial premises, whilst local councils investigate odour complaints for domestic and smaller commercial premises (such as restaurants).

Common Hotel Back of House Area Odours

Hotel back of house areas such as garbage / refuse rooms, loading docks, commercial kitchens, designated outdoor smoking areas or sewer vents, bio-treatment units and septic systems may be a common source of odour complaints.

Table 1: Common emission types and odourous gases

Odour Control Methods for Gaseous Contaminants

Basically to clean air from gaseous contaminants there are three (3) main mechanisms:

• Remove the source of the odour.

• Dilute and ventilate the air (clean while ventilating if ventilating to sensitive location) and replace with clean fresh air.

• Treat by providing an air cleaner which circulates air through itself to remove chemicals inside a closed space.

Odour Control for Garbage/Refuse Rooms

Several approaches exist to reduce odour in garbage rooms (using the above-mentioned principals):

• Make sure bins containing odour can remain closed as much as possible.
• Install a self-contained recirculating ioniser, whereby electrostatically charged ions are released into the area where it reacts with and destroy odour molecules and airborne infection present in ambient air.
• Install a self-contained recirculating ozone generator, which typically injects ozone into controlled space where it reacts with and oxidises odour particles in a chemical reaction which results in the production of carbon dioxide, water vapour and oxygen. Note: ozone generators must be controlled so there is sufficient residence time, and that no excessive ozone is present in occupied rooms for safety reasons.
• Install a self-contained recirculating gas-phase chemical media unit (such as a side access unit or corrosive air unit). Gas phase chemical media is used to target and adsorb contaminant gases.
• Increase room “Air Changes” by exhausting certain calculated volumes of air. The contaminated air should be cleaned, or diluted during extraction so the odour is not transferred to other areas. This can be achieved with gas-phase chemical media or with ozone generators.

Loading Dock Odours

The main way to reduce odour coming inside from loading docks:

• Change the location / system design with air intakes located away from the loading docks. If this is not possible, the air will need to be treated using a variety of odour and chemical based adsorption media. If carbon monoxide or dioxide levels are excessive, this will need to be dealt with via ventilation rather than treatment. Note: no treatment method that assures safety will be cost effective.
• Clean the supply air, so that fumes are treated at this supply stage and not transferred inside. This can be done with gas-phase chemical media filtration or with ozone generators. Note: ozone generators must be controlled so there is sufficient residence time, and that no excessive ozone is exhausted for safety reasons.
• Increase local air-changes and use positive pressurization or air curtains at building entry points to ensure fumes are not transferred inside.

Kitchen Odours

Kitchens are initially a source of generally pleasant odours, however, when exhausted into communal or residential areas, they may be found offensive due to odour, smoke, heat or other reasons. In general the approaches to this are:

• • Design to code to assure kitchen exhaust is of the right volumes and temperature.
  • Allow adequate and suitable make up air into the kitchen to avoid stalling the kitchen exhaust system or creating “fugitive” odours from the kitchen.
  • Locate air exhaust points away from sensitive areas and fresh air intakes and with good expectation of dilution by prevailing winds.
  • Treat odours, smoke and particulates with a staged and standards compliant approach. This may include UL rated high efficiency hood filters, adequate duct cleaning processes, treatment methods such as filters, odour absorbing activated carbon media or filters, ESPs and roof-top dilution fan exhaust systems.

Outdoor Smoking Area Odours

Exterior and less frequently, interior smoking rooms form a significant legal and OH&S challenge, however, the technical solution for the odour issues is well understood and established. This includes:

• • Enhanced room or area air changes and ventilation to remove smoke and odour.
  • Targeted extraction from “high-risk” areas, such as gaming tables in casinos.
  • Treatment and recycle systems involving electronic air cleaning systems like ESPs, air ionisation systems or particle filters and odour absorbing media.

In general, these systems will require custom design and large scale air volume movements, involving significant room for plant and equipment, so retro-fits are generally problematic.

It should be noted that any of these system will not avoid the inevitable health effects of primary smoke inhalation, and only reduce, but not eliminate, secondary inhalation effects.

Odours from Sewer Vents, Bio-Treatment Units and Septic Systems

Many “green-buildings” are taking opportunities to enhance their status with various local recycling systems for waste water and materials. The build up of odours in these systems is inevitable, and only hazardous in unusual, enclosed circumstances (e.g. Carbon Monoxide or Hydrogen Sulphide). In locations where hazardous levels have been identified, adequate sensing and alarm systems, such as carbon monoxide detectors, need to be allowed for in the design of systems.

In general, the ways that most of the “non-hazardous” odours are dealt with is by capture, treatment and then exhaust of the air:

• Controlled and targeted exhaust systems or hoods are used to collect fumes from the source, with adequate supplies of fresh air to replace, and the contaminated air removed.
• Treatment systems such as drum scrubbers, containing carbon, odour treatment media or bio filtration systems are all routinely used solutions with a variety of cost effectiveness profiles depending on the volume, nature and concentration of the odours.
• Exhaust of the odours to areas that will allow effective dispersion of the remaining odours from the treatment systems. Guidance is given to the location and nature of these exhaust points in various AS/NZS standards including 1668.2.

Final Thoughts

Odours are seldom hazardous, but should be taken seriously as they can often be an indicator of more significant problems located within the Hotel. This may include black mould from leaks or excessive carbon monoxide from diesel operation in inadequately ventilated areas.

Written by Jonathan Bunge (M.ENG Chemical), Shannon Roger (B.Ed) and Dr Allan Heckenberg (PhD) for Airepure Australia 2016.  Published in The Hotel Engineer, Volume 21 No 3, October 2016.

References

EPA Victoria

AS/NZS 1668.1: The use of ventilation and air conditioning in buildings. Part 1: Fire and smoke control in buildings: SAI Global 2015

AS/NZS 1668.2: The use of ventilation and air conditioning in buildings. Part 2: Mechanical ventilation in buildings: SAI Global 2012

Hvitved-Jacobsen T., Vollertsen J., Yongsiri C., Nielsen A.H., Abdul-Talib S: Sewer microbial processes, emissions and impacts, Aalborg University – Department of Environmental Engineering DENMARK, April 2002