Why Is Alcohol Not Used in Cleanroom Cleaning?

In casual life, the role of alcohol is viewed as being almost almighty, as a kind of collateral universal disinfectant: it sterilizes the germs in a flash, leaves the faint breath of vapor, and is a cheap commodity. However, alcohol is not preferable in high-standard practices of Clean Room Cleaning because it may be explicitly forbidden in the majority of high-quality cleanroom cleaning procedures.

This might sound paradoxical: why should alcohol be so unpopular in the products where the standards of cleanliness are so strict? The reasons explaining this shall be analyzed under safety, compatibility, and effectiveness of cleaning in this article.

What are the most common cleaning agents used in cleanrooms?

Isopropyl alcohol (IPA) is widely considered a good liquid for keeping cleanroom surfaces spotless. But what about methanol, ethanol, or butanol? Why not consider these types of alcohol for cleanroom cleaning as well? The answer depends primarily on performance, safety, and price.

Methanol and Evaporation

The vapor pressure of methanol is three times that of IPA at room temperature. This implies that methanol has a much higher evaporation rate, so cleanroom wipes cannot be kept damp enough to gather surface particles. Moreover, methanol requires higher vapor pressure, resulting in more alcohol being in the vapor form, exposing operators of cleanrooms to highly aggressive alcohol vapor.

Ethanol and Regulations

While ethanol, like methanol, has a much higher vapor pressure at room temperature than IPA (approximately 36%), its biggest issue is that it is a federally regulated substance.

Because some people drink ethanol, the federal government requires it to be denatured (i.e., rendered undrinkable by contaminating it with solvents such as methanol, isopropyl alcohol, acetone, methyl ethyl ketone, and methyl isobutyl ketone).

Using pure (undenatured) ethanol for wiping requires obtaining a government permit and complying with usage tracking procedures, which is much more cumbersome.

Butyl Alcohol and Solubility

Interestingly, butyl alcohol has a lower vapor pressure. As a larger molecule, its vapor pressure is about one-eighth that of IPA. However, issues arise from its odor and solubility.

Butyl alcohol's banana-like odor makes its long-term use unpalatable to most cleanroom operators. Furthermore, butanol's high hydrocarbon content limits its solubility in water to approximately 10% solution. In contrast, IPA is miscible with water at all concentrations.

Isopropyl Alcohol and Economies of Scale

Isopropyl alcohol is popular for cleaning applications across many different industries. In fact, its widespread use allows it to be produced in large quantities and at high purity levels. Its production volume and quality offer economies of scale. Its price advantage and availability make it an attractive option.

IPA also offers an appropriate balance between polarity (grease removal), vapor pressure (acceptable evaporation rate and odor), and miscibility with water. Consequently, isopropyl alcohol is often used with cleanroom wipes.

Why alcohol is not suitable for cleanroom cleaning?

1. Highly flammable, posing a safety hazard

Alcohol's most prominent drawback is its high flammability. This is especially true in high-ISO cleanroom environments (such as ISO 5 or ISO 6), where air circulation is rapid and electrical equipment is densely packed. Once alcohol evaporates and forms a gas cloud, even a small static spark can cause a fire or even an explosion.

Therefore, to ensure the safety of both operators and equipment, many pharmaceutical factories, semiconductor cleanrooms, and biological laboratories often avoid using flammable cleaning agents when designing their cleanrooms.

2. Rapid evaporation but prone to leaving residue

Alcohol may appear to evaporate quickly and dry cleanly on the surface, but in reality, it can easily leave behind invisible residue. If these trace residues are not thoroughly removed, they can affect downstream product quality. This is especially true in chip manufacturing or precision device production, where even submicron-sized particles can cause serious yield issues.

In contrast, more specialized cleanroom cleaners are often specially formulated to offer enhanced cleaning capabilities without leaving impurities on the surface that could affect cleanliness.

3. Poor material compatibility, easily damaging equipment

The equipment and materials used in cleanrooms are often made of polymer composites, stainless steel, or specialized coatings. Alcohol can react chemically with these materials and cause corrosion. For example, some plastic transparent observation windows or pass-through box panels may turn white, become brittle, or even crack in severe cases after contact with alcohol.

In professional Cleanroom Design, designers will select cleaning agents compatible with the material properties and usage environment, rather than simply relying on alcohol.

4. Alcohol cannot meet broad-spectrum disinfection requirements

Although alcohol is effective against bacteria and some viruses, it has limited effectiveness against more resilient contaminants such as spore-forming microorganisms and fungal spores. Cleanrooms, especially those handling pharmaceuticals and medical devices, have extremely strict microbial control requirements. Therefore, broad-spectrum disinfectants (such as quaternary ammonium salts and hydrogen peroxide) are often used in combination and rotated to prevent the development of drug resistance.