Can steam cleaners kill household germs?

Orders for steam cleaners have surged over the past month, since COVID-19 broke out in the UK, and stocks at many online retailers have sold out. 

With stores such as Currys PC World promising that steam cleaners deliver a 'deep, penetrating clean that eliminates germs and bacteria, helping to ensure a truly sanitised home', it's easy to see why so many people have ordered one.

But can steam cleaners really kill germs and help to keep you safe? In this guide, we'll tell you what you need to know and explain how to choose between different models.

Take a look at our steam cleaner reviews to see which aced our tough tests

How do steam cleaners work?

All steam cleaners work by heating water until it boils, thus creating steam.

This steam is very effective at cleaning surfaces as it's able to get in to cracks and pores that may not be accessible to normal cleaning cloths. The steam loosens dirt and grease, which can then be more easily wiped away.

Cleaning in this way is not just effective, but it also removes the need for harsh chemicals. This can be especially beneficial if your household contains babies or small children who like to put things in their mouths, as well as anyone with allergies that are affected by strong detergents.

Using steam cleaners to kill germs

Steam cleaners don't just remove surface dirt, they can also kill bacteria.

As the manufacturer, Shark, explained to us, they're able to do this as the temperature of the steam can be high enough to break down the internal structures of bacterial cells, preventing them from being able to survive or to replicate.

This makes them extremely effective. In fact, manufacturers typically say that steam cleaners will kill 99.9% of common household germs and bacteria, such as salmonella and E coli.

We don't check this in our lab assessments, but leading manufacturer, Karcher, told us that this figure has been independently tested and certified.

Are steam cleaners effective against COVID-19?

It's important to note that manufacturers' claims only cover household germs. Steam cleaners have not been specifically tested for their effectiveness at killing COVID-19, although Shark told us that, in theory, very high temperatures should have the same effect on viruses as they do on bacteria.

The current government advice is to clean your home with warm, soapy water and then to use household disinfectant, paying particular attention to frequently touched areas and surfaces, such as bathrooms and door handles.

However, it also acknowledges that 'when items can't be cleaned using detergents or laundered, for example, upholstered furniture and mattresses, steam cleaning should be used.'

Read our advice on how to clean your home effectively and for all our latest help and advice, visit our coronavirus hub.

How should you use a steam cleaner to kill germs?

If you're using a steam cleaner to kill germs, you need to use it in a specific way.

Shark gave us the following tips:

• If you're using a steam cleaner to blast steam directly on to a surface, then you must hold it close to the surface. Steam cools down quickly in the air, so if you're too far away from the target surface it may not be hot enough to be effective.
• And you need to give it a sustained blast. Although, unfortunately, there's no simple rule on how long you should do this for, because individual steam cleaners heat and disperse steam at different rates. We would advise that you take a little more time than you might usually, while being careful not to exceed the maximum time recommended in the instruction manual for that surface.

Shark also told us that steam mops, which disperse steam through a thick pad, work in a slightly different way. The mop head absorbs the heat energy from the steam, so the really high temperatures don't reach the floor surface itself.

However, the mop's hot, moist pad is very effective at wiping any bacteria away and removing it from the surface you're cleaning.

Temperatures in the pad may be sufficient to disinfect the mop head itself and kill any bacteria it has collected while it's actively steaming. However, you should wash the mop head thoroughly in a washing machine, according to the manufacturer's instructions, after you've finished (and before reusing) to remove any bacteria that may build up after use.

What can steam cleaners be used on?

Steam cleaners can tackle a wide variety of flooring, such as lino, vinyl, ceramic tiles and some laminate, as well as other surfaces such as kitchen units, showers and mirrors. And, as we've already noted, they can also be used to steam fabric and upholstery.

However, the steam they produce can cause damage to some materials, especially to unsealed wood floors as these can warp. Manufacturers often list the type of surfaces they say you can safely clean with their devices, but the information can be quite vague.

If in doubt, we would recommend that you check with your flooring manufacturer or installer.

What type of steam cleaner should I choose?

Steam cleaners come in a range of designs. Prices start from as little as £30 and rise to more than £400.

The type you should choose will depend on what you want to clean - if it's just a few kitchen tiles, then a cheap handheld cleaner will probably be sufficient. If you have loads of tiled floors to get through, then you may need a wheeled cleaner with a generous water tank.

Alternatively, upright cleaners with detachable handheld units are very versatile and can be used to clean a range of surfaces.

You can get more help on what type of steam cleaner to buy in our steam cleaner buying guide.

Popular steam cleaners

Below, we've pulled out three popular steam cleaners to suit different budgets and cleaning needs. To see all the models we've tested and choose the right one for you, head over to our steam cleaner reviews.

Hoover Steam Express SSNH1000, £39.99

• Type Handheld steam cleaner
• To be used on Small, hard-to-reach surfaces (but not large areas such as floors)
• Steaming time 8 minutes

This handheld steam cleaner is compact and lightweight, and can be used on a variety of surfaces, from oven grills to tiles. But can such a small steam cleaner successfully shift that tricky-to-reach dirt?

Vax Steam Fresh Power Plus, £99

• Type Two-in-one steam cleaner
• To be used on Hard floors and carpets plus harder to reach surfaces (via the detachable handheld unit)
• Steaming time 6 minutes

This flexible, two-in-one cleaner from Vax doubles as a steam mop and a handheld machine, thanks to the detachable, hand-held unit. It comes with a range of tools to attach to the handheld, making it suitable for cleaning surfaces around your home. Read our expert verdict on the Vax Steam Fresh Power Plus.

Karcher SC3 Upright Steam Cleaner, £200

• Type Upright steam mop
• To be used on Hard floors and carpets
• Steaming time 14 minutes

This is an upright steam cleaner that can be used to clean hard floors. Karcher models have typically impressed in our lab tests and the company claims that this model is its 'best-performing steam mop'. But does this model live up to to the manufacturer's claims? Find out in our review of the Karcher SC3 Upright Mop.

How Which? tests steam cleaners

We've tested steam cleaners for years and have reviewed all the models available from big names, including Black & Decker, Karcher and Vax, as well as a number of cheap own-brand models.

We don't specifically assess their effectiveness against bacteria, but can tell you which ones are the best for keeping your house spick and span.

And we don't just reveal the best models - we also highlight the low-scoring Don't Buy steam cleaners, so you can avoid buying a dud you'll soon be keen to replace.