Are there any safety concerns when using a Humidity Indicator Card?

If you’ve ever worked in industries that rely on protecting sensitive electronics, pharmaceuticals, or precision components from moisture damage, you’ve probably used a Humidity Indicator Card (HIC). These small, color-changing cards are ubiquitous in packaging for high-value goods—they let anyone inspect a package at a glance to confirm if moisture levels stayed within safe limits during shipping and storage. As a supplier who’s been working with HICs for over seven years, I’ve seen first-hand how often customers ask: “Wait, are these cards safe? Should I be worried about anything when I use them?” It’s a fair question, because when you’re protecting products that are critical to your business, you don’t want any hidden risks in the tools you use. Humidity Indicator Card

Let’s break down the real safety concerns related to HICs, separate fact from the myths, and walk through what you actually need to know to use them safely.

First, let’s get a basic understanding of what an HIC is, because that’s key to addressing safety. Most HICs have a white paper base, coated with a cobalt chloride-based indicator ink. Cobalt chloride is the standard for most industry-grade HICs because it’s reliable, affordable, and changes color sharply at specific humidity levels—usually 10%, 20%, 30%, 40%, 50%, or 60% relative humidity (RH). The indicator itself is cobalt(II) chloride, which is blue when dry, and when it absorbs moisture, it hydrates to cobalt(II) chloride hexahydrate, which is pink. Some newer formulations use non-cobalt indicators, like cobalt-free salts, for applications where even small amounts of cobalt are a risk.

Now, the main safety question people ask is: Is cobalt chloride toxic? That’s where a lot of the confusion comes from. Cobalt chloride is classified by several regulatory bodies as a possible human carcinogen, particularly when it’s inhaled as dust. But here’s the context that most resources don’t highlight for packaging applications: the amount of cobalt used in HICs is extremely small, and the ink is sealed onto the card base, so it’s not exposed to direct contact in normal use. Let’s look at the details. A typical HIC uses less than 0.1 milligrams of cobalt per square centimeter. To put that in perspective, a single card (which is usually about 5cm x 7cm, or 35 square cm) has less than 3.5 milligrams of total cobalt. That’s a tiny amount—less than the cobalt in a single multivitamin tablet, for example.

The risk of exposure comes only if the card is damaged, crushed, or incinerated. If you cut an HIC open, you might get a small amount of cobalt dust on your hands, but that’s easily washed off with soap and water. If you were to inhale that dust, which would only happen if you were grinding the card into fine powder and breathing it in, that would carry a risk. But for normal use—placing the card inside a package, sealing it, and disposing of the packaging after use—there is no meaningful exposure risk. Regulatory agencies like the U.S. OSHA and the EU REACH have specifically noted that HICs present no significant hazard during standard handling, because the cobalt is contained within a non-porous coating that prevents leaching or dust release.

That said, there are some edge cases where safety is a concern, and that’s where it’s important to know your application. For example, if you’re packaging pharmaceutical products that come into direct contact with food or drugs, you’ll need to make sure your HIC meets FDA food contact standards. Some cobalt-based HICs don’t meet these standards, because even trace amounts of cobalt could leach into a product if the packaging is damaged. For these applications, non-cobalt HICs are a better choice. They use materials like lithium chloride or other non-hazardous salts that are safe for direct contact with consumables.

Another edge case is for products used in medical devices that are implanted in the body. Even small amounts of cobalt can cause adverse reactions in some people, so manufacturers of implantable devices must use HICs that are 100% cobalt-free and biocompatible. I’ve worked with several medical device clients who switched from cobalt-based HICs to our non-cobalt formulations because their regulatory teams mandated it for implantable products. That’s a valid safety concern, but it’s not a flaw in HICs themselves—it’s a matter of choosing the right type of HIC for your specific application.

Another safety concern that comes up is leaching. Some customers worry that the indicator ink could seep out of the card and contaminate the product inside the package. Again, this depends on the type of HIC and the packaging material. High-quality HICs use a proprietary acrylic coating that locks the indicator salts into the paper base, so there’s no leaching under normal conditions. Cheap, low-grade HICs, on the other hand, might use a weak coating that can allow some leaching, especially if the package is exposed to high temperatures or humidity for long periods. I’ve had clients come to us after having issues with cheap HICs that left pink stains on their electronics, or that leached ink onto sensitive circuit boards. That’s a safety and quality risk, but it’s not a problem with HICs as a category—it’s a problem with poor-quality products from unvetted suppliers.

What about fire safety? HICs are made of paper and a small amount of chemical indicator, so they’re relatively flammable. But when used as intended, inside a sealed packaging, they don’t pose a fire risk. The amount of organic material in an HIC is negligible—less than 1 gram per card—so it won’t contribute significantly to a fire. However, if you’re incinerating packaging waste, HICs will release a small amount of chlorine when burned, which is a minor concern for air quality. But modern waste incinerators are equipped to filter out these emissions, so this is more of a facility-level concern than a risk for users.

Another common myth is that HICs are a choking hazard, especially for small children. HICs are small, but they’re rigid enough that they’re not easily broken into small pieces. That said, if you’re packaging goods that might be accessible to children, especially in households with young kids, you should ensure that the packaging is child-resistant, and that the HIC is not small enough to be a choking hazard. Most HICs are sized to prevent this, but it’s something to keep in mind for specific use cases.

Now, let’s talk about best practices to minimize any potential safety risks when using HICs. First, choose the right HIC for your application. If you’re packaging food, pharmaceuticals, or medical devices, go with a non-cobalt, food-contact grade HIC. If you’re packaging industrial electronics that don’t come into direct contact with consumables, a standard cobalt-based HIC is safe. Second, source your HICs from a reputable supplier, not a random discount vendor. Cheap HICs often use low-quality coatings, which can lead to leaching, inaccurate color changes, and even unsafe exposure if the ink is not properly contained. Third, handle HICs with basic hygiene: wash your hands after handling, avoid crushing or grinding them, and keep them away from open flames or direct heat sources. Fourth, dispose of HICs properly—either as regular waste (since the amount of hazardous material is negligible) or as part of your packaging recycling program.

I’ve seen how HICs have saved countless products from moisture damage, which can be far more costly than any minor safety concern. A single batch of electronics can be worth hundreds of thousands of dollars, and a single moisture-related failure can lead to recalls, lost revenue, and damaged reputations. HICs are a simple, cost-effective tool to prevent those losses, as long as you use them correctly and choose the right type for your needs.

For example, a client of mine who manufacturers hearing aids came to me two years ago with a problem. They were using a standard cobalt-based HIC for their packaging, and their quality control team found that some of the HICs were transferring pink color to the hearing aid casings, which were supposed to be clean and biocompatible. The hearing aid’s regulatory team flagged this as a potential issue, because even trace amounts of cobalt could irritate a patient’s skin. We recommended switching to our medical-grade, non-cobalt HICs, which use a lithium chloride indicator that doesn’t leach color or cobalt. After making that switch, the client had zero color transfer issues, and passed all their regulatory audits without any concerns. That’s the kind of difference choosing the right HIC makes—avoiding a safety risk without sacrificing the functionality of the card.

Another example is a client in the semiconductor industry. They ship high-end microchips that are extremely sensitive to moisture; even a small amount of moisture can cause the chips to fail. They were using cheap HICs from a different supplier, and had a 12% failure rate in their shipments, because the HICs were not accurate at their required 30% RH threshold. The HICs would sometimes change color too early, leading them to re-ship packages unnecessarily, or not change color when they should, leading to moisture damage. We supplied them with our high-precision cobalt-based HICs, which are calibrated to within ±2% RH, and their failure rate dropped to less than 0.5%. The safety concern here wasn’t toxicity—it was the risk of using an unreliable product that would damage their goods. That’s a critical point: safety concerns when using HICs often boil down to choosing a quality product that meets your specific needs, not a flaw in the technology itself.

So, to sum up: the most common safety concerns about HICs are often based on incomplete information. Cobalt-based HICs are safe for standard industrial use, because the cobalt is contained within a non-porous coating, and exposure only happens in extreme cases like crushing or incineration. For applications where cobalt is a concern, non-cobalt HICs are readily available and meet all regulatory standards. The real risks with HICs come from using low-quality products that don’t meet safety standards, or choosing the wrong type of HIC for your application.

Humidity Indicator If you’re evaluating HICs for your next project, or if you’ve had issues with HICs in the past, I’m here to help. I work with clients across industries to find the right HIC solution that meets your safety, quality, and budget needs. Whether you need cobalt-based HICs for industrial electronics, non-cobalt HICs for food or medical devices, or high-precision HICs for sensitive components, we can tailor a solution that works for you. Don’t let safety concerns hold you back from protecting your valuable products—reach out to discuss your requirements today.

References

1. Occupational Safety and Health Administration (OSHA). Cobalt and Cobalt Compounds. U.S. Department of Labor, 2022.
2. European Chemicals Agency (ECHA). REACH Registration Dossier for Cobalt Chloride, 2021.
3. Food and Drug Administration (FDA). Food Contact Substances: Indicator Inks for Packaging, 2020.
4. International Organization for Standardization (ISO). ISO 17514:2018, Packaging – Humidity Indicator Cards – Specification and Test Methods, 2018.
5. World Health Organization (WHO). Environmental Health Criteria 222: Cobalt and Cobalt Compounds, 2000.

Dongguan Weiyi Electronic Technology Co., Ltd.
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