What Is That Horrible Smell?

| Sep 3, 2021 10:00:00 AM

Customers and users of freshly laundered textiles have a justified expectation that because they have just been washed, they will be clean, disinfected and stain-free.

One way of giving the lie to this assumption is if the items give off an unpleasant odour. Even worse, if an unpleasant smell has been allowed to develop into a foul, stomach-churning stench then the launderer can be in real trouble!

The present pandemic has heightened everyone’s sensitivities and there could not be a worse time to be experiencing odour complaints.

This month we look at how to tackle these when they arise.

Identifying the type of odour

In World War 1, some troops were taught to recognise poison gas by its initial smell from a rhyme that included the lines:


‘Phosgene smells like mouldy hay,
Chlorine takes the breath away!’

Not every soldier would recognise the smell of mouldy hay, but they quickly came to realise when chlorine was being used from the gasp produced when it was encountered.

There is negligible risk of being poisoned by the traces of chlorine on over-bleached textiles, but leading launderers will still occasionally sniff the finished goods in the packing area to check that no one is dosing bleach incorrectly. It also acts as an early warning for any other odour complaint!

If an odour complaint appears to be very faint (not everyone has a good sense of smell), then it often pays to rub the fabric together to create a warm area, just like the body heat would from the wearer of a smelly garment. This will magnify the odour considerably and aid rapid identification.

Foul, dank sewer smells tend to be produced by unremoved protein soiling and staining from foodstuffs. These can get much worse when bacteria start to breed on the residues, leading to complaints from users of industrial workwear who experience a horrible stench when they open their locker door to remove a fresh garment.

‘Fish and chip’ odour complaints are usually associated with incorrect neutralisation or rinsing of peracetic acid, used in some laundry processes because of its disinfection and stain removal properties. The odour closely resembles that of vinegar sprinkled liberally in fish and chip shops, in the UK and in many other countries, which gives rise to the customer’s suspicion that the items have not actually been washed at all!

Vomit smells are from the chemical butyric acid, which gives vomit its odour. They do not usually survive laundering unless the launderer is using a neutral detergent followed by inadequate rinsing.

‘Sooty’ or ‘dusty’ odours often arise if textiles contaminated with soot, quarry dust or particulate foodstuffs, such as flour, are processed with inadequate detergent dosage or inadequate rinsing.

Mineral oils and light fuels such as petrol or diesel usually give a readily recognisable smell and can be cured by adjusting the detergent dosage.

Excess chemical smells

The most common odour complaint caused by residual chemicals on the fabrics is that caused by bleaching using sodium hypochlorite (‘chlorine bleach’).

If this is not thoroughly rinsed off or otherwise neutralised, then even a tiny amount left behind produces a distinct chlorine odour reminiscent of swimming pools or toilet cleaner.

Residual chlorine odour should ring alarm bells for the launderer for two reasons:

Firstly, there is a real risk that the smelly stock is being slowly degraded and prematurely weakened and will start to show holes and tears shortly because excess chlorine bleach rots cotton and linen.

Secondly, someone is probably over-dosing with chlorine bleach to cure a problem with resistant stains and this is the wrong cure. Vegetable dye stains from tea, coffee, beer and red wine, for example, are easily removed by chlorine bleach, so any residual stubborn stains are probably from oxidised proteins such as blood and animal fats from gravy or meat juices or oily fish or dairy products. These are cured going forward by getting the pre-wash conditions right (at least 4 minutes at below 40C - 38C is ideal).

Bacterial odours

Some smells, especially those from unremoved protein soiling and staining, can get much worse after a few hours in a warm pile of finished goods or in the locker of the user of industrial or food-industry workwear.

This is often the result of bacterial growth on the nutrition provided by the unremoved substances, a small amount of which can support many millions of tiny micro-organisms. It is the excrement from these which produces the characteristic foul odours.

Health services in many countries still rely on implied thermal disinfection for controlling the level of bugs on healthcare textiles. Typically, this calls for a process in which the main wash is held at a minimum of 71C for 3 minutes plus mixing time.

There is a mistaken belief that this can also be achieved in the laundry ironer or garment tunnel finisher or garment press, which are at much higher temperatures. In practice, it has been found that enough bacteria can survive in the damp seams or hems to breed when the fabric cools. If there is nutrition available in the form of residual protein soiling, then the breeding is prolific and very foul odours can result. Disinfection should occur in the wash process itself, followed by rinsing in clean water.

This is made much worse if the rinse water is drawn from surface sources such as a river or stream. If this happens to flow through a field of animals, then the risk is much greater and this can be the origin of odours that can be really stomach-churning.

The best way a launderer using surface water, instead of mains water, can monitor this is by the use of simple dip-slides on at least a weekly basis. These cost only a few pounds each and can be read in-house, without the need for an external laboratory, and the necessary brief training is readily available.

Sooty and dusty odours

The human nose is very sensitive and can detect the odour of soot near a recently swept chimney from very few particles of carbon left on a fabric left near the fireplace. These might be too small to be visible to the naked eye (they can be seen with a strong magnifying glass) but the nose will still detect them very readily!

The solution to these and other dusty, particulate odours lies in the choice of detergent. The key ingredient is the ‘suspending agent’. Most detergents contain a certain amount of this, which is designed to wrap around the exposed part of any particle embedded in the cloth surface and help to pull it off. Then, once the particle is in the wash liquor it wraps around it completely to stop it from re-depositing back onto the fabric.

This is achieved in two ways:

Firstly, the suspending agent will physically prevent it from going back onto the material.

Secondly, it will neutralise the small electrostatic charge on the particle, which would otherwise make it gravitate towards the oppositely charged cloth surface.

Premium detergents usually carry more suspending power than the cheaper ones, which rely more on the surfactant. The increase in effectiveness can be achieved either by using a higher percentage of suspending agents in the blend or by incorporating more powerful suspending agents or both.

It is possible to purchase an extra suspending agent as an additional additive for a laundry faced with heavily contaminated contract work of this type, to offer a valuable competitive edge.

Washer extractor selection

The only washer-extractors that currently offer unrivalled solutions to odour management are ones featuring XTendTM technology (a combination of XOrbsTM and XDrumTM). These commercial washing machines address the problem of odours associated with the poor removal of fatty, oily protein soiling and staining in a variety of ways.

Firstly, it uses XOrbsTM in the main wash and pre-wash stages, the surface of which is ‘oleophilic’. It is designed to attract fats and oils to be adsorbed onto the surface, reducing reliance on detergency alone.

Secondly, the XOrbsTM displace the need for around half of the water required by a conventional wash process. This enables higher concentrations of detergent (and the surfactant and suspending agent to contains) to be employed, whilst still lowering the chemicals cost significantly when compared with normal was processes. This enables unrivalled quality at measurably lower wash cost and the side benefit of a much lower environmental footprint (through much lower discharge of chemicals to drain).

Conclusion

Achieving consistently high quality with no odour problems and negligible complaints is never going to be easy, but when all the customer can talk about is the price it is useful to have something else to raise. The successful launderer needs to achieve consistent high quality at a cost low enough to make a sensible profit and by understanding and reacting to the points raised in this month’s blog we have tried to indicate ways of doing this.

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