Nitric Acid Fume Hood

A fume hood is absolutely critical for working with nitric acid. As a strong oxidizer and highly corrosive acid, nitric acid presents significant hazards from its vapors, which can cause severe damage to the respiratory tract and skin. A fume hood's ventilation system actively pulls these harmful fumes away from the user and out of the laboratory.

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Hazards of Nitric Acid

 

• Corrosive: Nitric acid can cause severe burns to skin and eyes, and is extremely destructive to mucous membranes and the respiratory tract.

• Oxidizer: It reacts violently with many organic materials and other incompatible substances, which can lead to fires or explosions.

• Toxic Vapors: Concentrated nitric acid releases toxic reddish-brown nitrogen dioxide (NO2​) fumes, which are highly hazardous if inhaled. These vapors are also corrosive and can damage equipment and surfaces.

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Fume Hood Best Practices

 

Using a fume hood correctly is the primary safety measure for handling nitric acid.

• Check Airflow: Before starting, confirm that the fume hood is operating properly. Look for a monitor or airflow indicator, or use a "Kimwipe" to see if the air is being pulled inward.

• Sash Position: Keep the sash at the lowest possible height to provide a physical barrier and ensure optimal airflow.

• Work 6 Inches Inside: Place all equipment and containers at least 6 inches (15 cm) back from the front edge of the hood to prevent fumes from escaping.

• No Clutter: Do not store excess chemicals or equipment in the fume hood, as this can disrupt airflow and reduce its effectiveness.

• Keep Your Head Out: Never place your head inside the fume hood while working with chemicals. Your hands and arms should be the only things inside the workspace.

• Use Proper Materials: Since nitric acid is so corrosive, a standard fume hood may not be sufficient. Special acid-resistant fume hoods are often constructed with corrosion-resistant materials like polypropylene or PVC liners and tempered glass sashes.

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Required Personal Protective Equipment (PPE)

 

Using a fume hood is not a substitute for proper PPE. The following are essential when working with nitric acid:

• Gloves: Nitrile gloves offer limited protection and are not recommended for concentrated nitric acid. Instead, use gloves made from materials like Viton or butyl rubber, which provide superior chemical resistance. Always inspect gloves before use and change them immediately if there is a splash or spill.

• Eye and Face Protection: Wear chemical splash goggles and a face shield.

• Body Protection: A lab coat, long pants, and closed-toe shoes are the minimum. A chemical-resistant apron is also highly recommended.