Formaldehyde Detection in Hospitals – A Mission for Champions of Health!

Introduction

Formaldehyde (chemical formula: CH₂O, CAS No.: 50-00-0) is the second smallest molecule in the functional group of aldehydes, following only formyl fluoride. It is a colorless gas at room temperature with a pungent, irritating odor and is highly flammable. Due to its volatility and reactivity, it poses both health and safety risks, with a time-weighted average (TWA) exposure limit of less than 0.5 ppm, reflecting its classification as a hazardous substance.

With an annual global production volume exceeding 20 million tons, formaldehyde ranks among the most extensively manufactured industrial chemicals. Its versatility makes it a key component in a wide range of applications across multiple industries:
 

• Starting agent for polymerization reactions: Formaldehyde is a crucial precursor in the production of various synthetic resins, including urea-formaldehyde, phenol-formaldehyde, and melamine-formaldehyde resins. These materials are widely used in the manufacture of particleboard, plywood, laminates, and insulation materials. 
• Preparation of anatomical specimens: In biological and medical sciences, formaldehyde is commonly used as a fixative to preserve tissue samples. It stabilizes biological tissues by cross-linking proteins, which prevents decay and maintains structural integrity for microscopic examination and long-term storage. 
• Sterilization and disinfection: Due to its potent antimicrobial properties, formaldehyde is employed as a disinfectant and sterilizing agent, particularly in hospital settings and laboratories. It is effective against bacteria, fungi, and viruses, and is used to sterilize surgical instruments, rooms, and even biological safety cabinets.
   

Despite its widespread utility, formaldehyde is classified as a carcinogen by several health agencies, including the International Agency for Research on Cancer (IARC). Therefore, its use is strictly regulated, and exposure must be carefully controlled in occupational and consumer environments.

When used as disinfectant, it is crucial to maintain personal safety in hospitals and sanitary institutions. In such facilities alcohols are also widely used for cleaning or hand sanitation. Fixed gas detection systems often use electrochemical sensors for CH2O detection. Those sensors can have strong cross sensitivities towards alcohols and result in false readings

The customer challenge

Fixed gas detectors are commonly installed in hospital sterilization rooms to monitor indoor air quality, particularly for hazardous substances like formaldehyde. However, alcohol-based agents such as ethanol and isopropanol—frequently used for surface cleaning and hand sanitization—can interfere with electrochemical sensors. These substances often trigger unstable readings and false alarms.

For hospitals, this presents a significant challenge. False alarms result in longer waiting times before staff can re-enter sterilized areas, delaying critical processes such as the cleaning of  surgical instruments. These delays negatively impact operational efficiency and staff workflow.

A regional hospital reported in an interview that its surgical equipment cleaning facility was underutilized by approximately 32% due to frequent false alarms from its formaldehyde detector. To mitigate this, the gas detector manufacturer had to dispatch service technicians for regular on-site checks, incurring additional costs. Ultimately, the hospital paid several thousand Swiss Francs annually for unplanned service visits and downtime—an avoidable expense with more accurate sensor technology.

The solution

For electrochemical sensors, improving selectivity toward the target gas is a critical objective—especially in environments where interfering substances, such as alcohols, are frequently present. Various strategies exist to enhance selectivity, including:
 

• Use of onboard filters 
• Integration of a fourth (auxiliary) electrode 
• Specialized sensor configurations
   

However, when it comes to selective detection of formaldehyde (CH₂O) in the presence of alcohols like ethanol or isopropanol, common solutions fall short. Due to the high reactivity of formaldehyde, onboard filters are ineffective. Compensation via a fourth electrode is also not feasible in this case. Membrapor, a Swiss manufacturer of electrochemical sensors, has chosen the latter variants to solve this customer challenge. This resulted in the CH2O/CA-10, with A standing for highly selective. This sensor type has a special setup to discriminate alcohols. It uses a combination of specialized electrodes and a bias voltage to reduce the effect of alcohols. The field tests have shown an excellent performance! There have been no more false alarms saving the gas equipment manufacturer and end customer time and money.