How to spot hidden surveillance: Staying safe in your holiday rental

When planning a holiday trip, we often face the dilemma of choosing the right accommodation. There are many options – from hotels and apartments to rooms for rent. However, it is essential to consider safety, especially if spying devices and two-way mirrors are installed in such places. Learn how to recognise them.

Safety should be a priority when choosing a hotel, apartment, or other type of accommodation. Unfortunately, owners sometimes place various monitoring devices that can violate privacy.

The most commonly encountered are small, hidden cameras, but there are also more subtle surveillance methods, such as unique mirrors known as two-way mirrors. Although they are relatively rare, their presence in a rented room cannot be ruled out.

Two-way mirrors, also known as one-way mirrors, work on the principle of reflecting only a portion of the light while the rest passes through the glass. This effect is achieved with a thin layer of metal—usually aluminium—applied to the mirror surface. Typically, one of the rooms adjacent to such a mirror is well-lit, while the other remains semi-dark.

At first glance, two-way mirrors look like regular mirrors. This is because the human eye has difficulty detecting light from a less well-lit area. However, people in the darker room can freely observe what is happening in the brightly lit interior.

Spying is commonly considered a severe violation of privacy. Discovering a two-way mirror in a rented room raises understandable concerns and suspicions about the owner's intentions. The uncertainty of whether we are being recorded or photographed can be particularly unsettling.

Upon arriving at the accommodation, performing a simple test using a marker or fingernail to identify a two-way mirror is worth it. A video showing how to do it can be found on TikTok. The link is below.

If you see two lines (the one drawn with a marker and its reflection) on the mirror's surface, you are dealing with an ordinary mirror. However, if you see only one line, it may indicate a two-way mirror. A similar method can be used with a fingernail – if you see a gap between the nail and its reflection, it is an ordinary mirror. The absence of a gap suggests a two-way mirror.

However, remember that factors such as the type of lighting or the material of the mirror can alter the image's perception.

Another way to check the type of mirror is to use a torch. Turning off the lights in the room and pointing a torch from a mobile phone at the mirror can reveal the space behind it, confirming the presence of a two-way mirror.