You want to enjoy cool air as it is extremely hot, but the cool air created by your air conditioner does not reach you. It is just wasting electricity.

The same goes with negative ion generators. If negative ions do not reach you, the generator is wasting electricity. Some negative ion generators generate negative ions but only very few reach you.

Negative ion counts are generally measured in (pcs/cc). You cannot evaluate performance of negative ion generators with this value only.

For example, a negative ion generator which generates 1,000,000 (pcs/cc) can be good or not so good. This is because the distance from the generator where this amount of negative ions can be detected is not shown.

Negative ion counts dramatically decrease as you go further away from the generator. There are products which emphasize the ion count detected at the blow off point while very few can be detected at 50cm away. This is why you need to pay attention to the distance.




The ion count at a distance away from the generator determines the performance of the generator.

The ion count detected at a certain distance away from the ion generator shows you how far negative ions travel.

You need to pay attention to the ion count at least in the blow off direction because most manufacturers do not provide ion count information in angled directions. It would be ideal if negative ion counts in the both directions were always available.




If the ion count at 1m away from the ion generator is below 10,000 (pcs/cc), the performance is not so good.

Ion count: Performance (for your reference)

• 300 (pcs/cc) at 50cm: Poor
• 3,000 (pcs/cc) at 50cm: Not so good
• 20,000 (pcs/cc) at 1m: Good
• 100,000 (pcs/cc) at 1m: Very good

As we mentioned in "Pay attention to the distance from the negative ion generator!", negative ion counts dramatically decrease as you go further away. The same goes with angled directions.

It is possible that almost no negative ion molecule can be detected in the 30 degree direction. If you have such an ion generator, you always have to stay in the blow off direction in order to enjoy negative ions.




While cool air created by your air conditioner spreads throughout the room as time passes and temperature goes down, ion counts do not dramatically increase as time passes because negative ions vanish quickly. This is why negative ions need to spread in every direction.

As mentioned above, a negative ion generator, which disperses negative ions to the blow off direction only, is not good for practical use. However, many models fail to perform this task because of technical difficulties. This is why you have to make sure that negative ions spread in every direction because you are not always in front of the generator.

Here is how to make sure that negative ions spread in every direction.

Coverage area




The coverage area is often decided by the manufacturer itself with no industry standard, so it is just for your reference.

Negative ion distribution
The negative ion distribution data shows how the ions spread. This data is not always available because very few companies disclose it. Here is the ion distribution data of the Medical Ion Mini.



Figures vary depending on air purification levels and other ambient conditions.

It is ideal to see how negative ions spread with the actual ion counts.

A negative ion generator which looks nice, powerful or is recommended by Professor xxxxx does not always perform well. The performance is more important.

Appearance is important as your negative ion generator stays in your room but you have to pay more attention to the performance.

As we mentioned in "How far negative ions travel" and "How widely negative ions spread out", the negative ion distribution data is very important.

If you can only find the negative ion count detected at the blow off point or at an unknown distance, you should contact the manufacturer for more information. Otherwise, you may end up with a quasi-ion generator.

Specification item	Example	Importance
Negative ion count (blow off direction)	20,000,000(pcs/cc at 0cm) 1,000,000(pcs/cc at 50cm) 700,000(pcs/cc at 100cm)	High

Ion counts in blow off direction show you "How far negative ions travel". You cannot evaluate performance of negative ion generators without negative ion count information.

It is possible that some million negative ion molecules are detected at the blow off point but very few can be detected at 50/100/200cm away.

If only less than 2,000-3,000 (pcs/cc at 1m) negative ions can be detected, the performance of the ion generator is not good and it is only good for mobile or other special use.

Not only ion counts in the blow off direction but also those in angled directions (found on the next page) are an important factor.

Specification item	Example	Importance
Negative ion count (angled directions)	500,000(pcs/cc in 30 degrees at 2m) 150,000(pcs/cc in 90 degrees at 2.5m) 10,000(pcs/cc in 180 degrees at 1m)	High

Ion counts in angled directions show you "How widely negative ions spread out". It is a very important factor to choose the best negative ion generator but very few manufacturers disclose it.

If very few negative ions can be detected in angled directions, the ion generator is just wasting electricity.

We suggest you should pay attention on how widely negative ions spread out.

Specification item	Example	Importance
Maximum coverage area	40 m2 (430 ft2)	High

A maximum coverage area is just for your reference because it is decided by the manufacturer with no industry standard. We suggest you should choose the negative ion generator which covers the widest area possible.

It is ideal if negative ion count info in angled directions is available as it shows you how the ions can be distributed.

Specification item	Example	Importance
Life span	5 years+	High

We believe you want to purchase a product which can perform well for long periods.

Generally, ionizing needles determine the life span of negative ion generators which incorporate the discharging method.

Worn-out ionizing needles can cause lower ion counts or generation of highly concentrated ozone.

Before you purchase a negative ion generator you need to know the life span and how it is determined.

Specification item	Example	Importance
Safety measures	Safety circuit, Ozone/EMI suppression	High

Negative ion generators, which incorporate the discharging method, have internal circuits where high voltages are used. For your safety, we suggest you should choose a generator which is designed to prevent you from touching these circuits.

Some generators produce harmful ozone gas as the ionizing needles get worn out.

You should choose a safe product.

Specification item	Example	Importance
Purification capability	98% of 0.1-0.3micron particles removed in 5 minutes	High

Negative ions combine with dust and particles floating in the air and fall to the floor. As the result, the dust and particles no longer exist in the air. This is how the air is purified by negative ions.

Air purification capabilities are an important factor when choosing the best negative ion generator.

A negative ion generators, which can disperse plenty of negative ions throughout the room, has a high ability to remove dust and particles floating in the air.




Air purification capabilities are an important factor when choosing the right product but manufacturers do not always provide this information.

Specification item	Example	Importance
Stable performance	Designed to maintain performance under extreme conditions	Middle to High

Temperature and humidity changes can significantly lower the performance negative ion generators which employ the discharging method.

You should choose a negative ions generator which is designed to maintain optimum performance under low/high temperature. Otherwise, it will not perform well under such conditions because the negative ion counts can dramatically drop.

This image shows you the Medical Ion Mini maintains optimum performance under temperature and humidity changes.




Very few products in the market are designed to maintain performance under extreme conditions.

Specification item	Example	Importance
Life span of ionizing needles	5 years+	Middle

The life spans of negative ion generators which employ the discharging method are usually determined by the ionizing needles.

Ionizing needles gradually get worn out as a result of repetitive charging/discharging or by chemical reactions.

Worn out needles can lower negative ion counts or produce a lot of harmful ozone.

The life span of ionizing needles is an important factor because it determines the life span of the negative ion generator.

Specification item	Example	Importance
Positive ion counts	0(pcs/cc)	Middle

Negative ion generators can generate both positive/negative ions simultaneously, particularly if they employ the corona discharging method.

Positive ion generation lowers negative ion counts because they are cancelled out by their positive counterparts.

It is ideal not to produce positive ions.

Specification item	Example	Importance
Ozone production	0.001ppm or less	Middle

Most of negative ion generators which employ the discharging method generate negative ions and ozone simultaneously.

Ozone gas is used for sterilizing/deodorant purposes but it is harmful to the human body if it is highly concentrated. The safety limit set by the Ministry of Health, Labour and Welfare is less than 0.1ppm (in working areas).

Basically, a negative ion generator, which does not meet the safety standards, is not sold in the market. However, worn out ioznizing needles can generate highly concentrated ozone.

Ozone itself has no odor but it can give off an offensive stimulating smell when it reacts with other substances in the air. You have to choose a product which meets safety standards and make sure if it does not give off the odor caused by the reaction if you do not like the smell.

Specification item	Example	Importance
Test operation	Comes with the ion detector for test operation	Middle

You cannot tell if your negative ion generator is working properly because you cannot see ions with the naked eye.

A negative ion generator which has a built-in indicator light and/or comes with a detector is ideal because they assure you that it is generating negative ions.

Specification item	Example	Importance
Maintenance	Cleaning of the ionizing needles	Middle

Maintenance procedures vary depending on the negative ion generator.

Some products require you to clean the ionizing needles or replace the filters on a regular basis, while those which generate negative ions by crashing water require you to clean/refill the water tanks.

You should know what maintenance work is required to maintain the performance before you purchase the negative ion generator.

Specification item	Example	Importance
Purchase of consumables	Not needed	Middle

Some negative ion generators require you to purchase filters or other consumables on a regular basis.

You should know the expenditures before you purchase the generator because you have to continue to pay as long as you use it.

Specification item	Example	Importance
Wind noise generation	No noise due to no fan	Middle

Some negative ion generators have built-in fans/motors.

We suggest you should know the noise levels generated by the generator before you purchase it because you may be disturbed by the noise.

There are several factors to consider when choosing the best negative ion generator. The most important factor is if negative ions reach you or not.

However, many manufacturers do not provide this most important information.

Negative ion count information in the blow off and angled directions shows you if the negative ions reach you.

For example, "Massive negative ions!" or "2,000,000 pcs negative ions!" does not ensure that the negative ions reach you.

Coverage areas are just for your reference only because there is no industry standard.
We suggest you should make sure that the negative ions will reach you before you purchase the product.