Salt is hygroscopic. Under conditions of increased relative humidity, the salt absorbs the water in the air. In the case of a lamp, the moisture-filled salt is next warmed by the light bulb. As a result, it will then only emit highly negligible quantities of sodium and chloride ions, far lower than those found in a working salt mine or by the sea.

Comparing the atmosphere around a salt lamp with that of coastal regions, areas around saline graduation towers or the previously mentioned mines is therefore by way of being metaphoric and designed more for marketing purposes than actually corresponding to reality.

The most beneficial conditions prevail on the coast and in forests, where the quantities of positive and negative ions are more or less the same, at around 1 000 particles per 1 cm3. In contrast, the same volume of air in indoor residential spaces contains between 100 and 300.

Ionisation can be confirmed by means of an instrument known as an ion metre. Experiments have demonstrated that an increased concentration of small ions only occurs in the immediate vicinity of a salt lamp. So the ionising effect of using these lamps should really not be overrated. The best way of equalising the ions in a room is by airing it regularly.

Devices known as ionisers are used to ionise the air in rooms with a preponderance of positive ions. They suck the positive ions out of the air and emit negative ones.

The latter are created by means of either high voltage or thermal radiation; in other words the emission of slow electrons from heated metal. The second method produces a better effect because there is no emission of even trace quantities of ozone, a harmful gas which is a side effect of the process of high-voltage ionisation.

Air ions generated by means of thermal emission are exceptionally beneficial to the health because they are large and viable, with the negative charge enclosed inside. In a word, they are the most similar to those created by nature. Air rich in these ions occurs primarily by the sea, in coniferous forests, in the vicinity of waterfalls and in working salt mines.

Inhaling negative ions improves the sense of well-being, enhances concentration and resistance to post-operative pain and accelerates the healing of wounds. It also works to speed up biological reactions. Positive ions slow down the course of post-operative healing at the cell level. In excess, though, they trigger a sense of malaise, increased oxygen consumption, headaches and so forth.

However, it should be remembered that, while negative ions reduce the healing time for wounds, at one and the same time, they speed up the growth of neoplasms. So artificially ionised air need to be used with caution.

The balance of ions in the air can safely be improved by frequently airing rooms and by burning an open flame. Measurements should be taken before using ionisers, as this makes it possible to select the right equipment for local conditions. Devices for creating negative ions are highly productive and often exceed nature’s norms by a thousandfold.

However, the balance of ions in the air can safely be improved by frequently airing rooms. Or by burning an open flame, which can certainly be more appealing.