Nitric acid is a highly corrosive mineral acid with the chemical formula HNO3. It is colourless to yellowish in its pure form and has a sharp, choking odour. In Canada, nitric acid is used in industrial and laboratory settings — but accidental exposure can cause serious harm to your skin, eyes, lungs, and digestive system. This article explains what nitric acid is, how it affects the body, and what to do if you or someone you know is exposed.
What Is Nitric Acid?
Nitric acid is one of the strongest acids known to science. Its chemical formula is HNO3, meaning each molecule contains one hydrogen atom, one nitrogen atom, and three oxygen atoms.
In its concentrated form, nitric acid releases toxic fumes. These fumes can irritate and damage the respiratory tract even without direct skin contact. Even a brief exposure to high concentrations can be dangerous.
In Canada, nitric acid is commonly used in fertiliser manufacturing, metal processing, and chemical laboratories. It is also found in some cleaning products used in industrial settings. However, it is not a substance the average Canadian encounters in everyday life.
Pure vs. Dilute Nitric Acid
Pure, concentrated nitric acid is extremely dangerous. Dilute forms — mixed with water — are less immediately harmful but still corrosive and capable of causing chemical burns over time.
Both forms can damage living tissue. Therefore, any form of nitric acid should be treated with caution and handled only by trained professionals with proper safety equipment.
How Nitric Acid Affects the Body
When nitric acid comes into contact with the human body, it reacts chemically with skin and tissue. This reaction happens quickly and can cause serious injury within seconds. The severity of the damage depends on the concentration of the acid and how long it stays in contact with the body.
The acid causes what is known as a chemical burn. Unlike a heat burn, a chemical burn can keep damaging tissue even after the source is removed. This makes it especially important to rinse the affected area with water immediately.
Skin Contact
Contact with nitric acid causes the skin to turn yellow or orange. This happens because the acid reacts with proteins in the skin — a process called xanthoproteic reaction. The affected area quickly becomes painful, inflamed, and blistered.
In severe cases, the chemical burn can penetrate deep into tissue. Scarring and long-term skin damage are possible, especially if treatment is delayed.
Eye Contact
Nitric acid is extremely dangerous to the eyes. Even a small splash can cause intense pain, redness, and temporary or permanent vision loss. Immediate flushing with clean water for at least 15 to 20 minutes is critical.
After flushing, the person must go to an emergency room right away. Do not wait to see if the pain improves on its own.
Inhalation of Fumes
Breathing in nitric acid fumes can damage the lungs and airways. Symptoms of inhalation exposure include coughing, choking, chest tightness, and shortness of breath. In serious cases, it can lead to a condition called pulmonary oedema — a dangerous buildup of fluid in the lungs.
Symptoms of lung damage may not appear immediately. In some cases, they develop hours after exposure. For this reason, anyone who has inhaled nitric acid fumes should be monitored by a medical professional, even if they feel fine at first.
Swallowing Nitric Acid
Accidental ingestion of nitric acid causes severe burns to the mouth, throat, and stomach. Symptoms include intense pain, vomiting, drooling, and difficulty swallowing. This is a life-threatening emergency.
Do not try to make the person vomit. Call 911 immediately and contact the Poison Control Centre. In Canada, you can reach poison control by calling 1-844-POISON-X (1-844-764-7669) or visiting your provincial health authority’s website for the local number.
Signs and Symptoms of Nitric Acid Exposure
Recognising the signs of nitric acid exposure quickly can make a big difference in outcomes. Symptoms vary depending on how a person was exposed — through the skin, eyes, lungs, or digestive system.
Common symptoms include:
Yellow or orange staining of the skin at the point of contact
Severe burning pain at the exposure site
Blistering and swelling of the skin
Redness, tearing, and pain in the eyes
Coughing, wheezing, or difficulty breathing
Chest pain or tightness
Nausea and vomiting if swallowed
Dizziness or confusion in cases of heavy fume inhalation
Furthermore, symptoms from inhaled fumes can be delayed. A person may feel only mild discomfort at first, then develop serious breathing problems hours later. Therefore, always seek medical attention after any known exposure.
First Aid for Nitric Acid Exposure
Acting fast is essential when someone is exposed to nitric acid. The goal of first aid is to remove the acid from the body as quickly as possible and to limit further damage.
Skin Exposure: What to Do
Immediately remove any clothing or jewellery that may have been contaminated. Rinse the affected skin with large amounts of cool running water for at least 20 minutes. Do not scrub the area — gentle flushing is enough.
After rinsing, cover the area with a clean, dry bandage or cloth. Then go to an emergency room or walk-in clinic as soon as possible. Do not apply creams, ointments, or home remedies before getting medical advice.
Eye Exposure: What to Do
Flush the affected eye immediately with clean, lukewarm water. Hold the eye open and allow water to run over it continuously for at least 15 to 20 minutes. Remove contact lenses if it is safe to do so without delaying the rinse.
After flushing, go directly to an emergency room. Eye injuries from acid exposure are considered emergencies. Time is critical to protecting your vision.
Inhalation: What to Do
Move the person away from the source of fumes immediately. Get them into fresh air as quickly and safely as possible. If they are having trouble breathing, call 911 right away.
Even if the person seems to be recovering, they should be assessed by a doctor. As noted above, lung damage from acid fumes can appear hours after the initial exposure.
If Swallowed: What to Do
Call 911 and poison control immediately. Do not give the person anything to eat or drink unless directed by poison control. Do not induce vomiting, as this can cause additional burns to the throat and mouth.
Keep the person calm and still while waiting for emergency services. If the person becomes unconscious and stops breathing, begin CPR if you are trained to do so.
Nitric Acid Safety in the Workplace
In Canada, workplace safety around hazardous chemicals like nitric acid is regulated under provincial occupational health and safety legislation. Employers are required by law to provide workers with proper training, protective equipment, and safe handling procedures.
Workers who handle nitric acid should always wear appropriate personal protective equipment (PPE). This includes chemical-resistant gloves, a face shield or safety goggles, a lab coat or chemical-resistant apron, and in some cases, a respirator.
In addition, all workplaces that use nitric acid must have a Safety Data Sheet (SDS) readily available. The SDS outlines the hazards of the chemical and what to do in an emergency. Workers have the right to read and understand this document. For more information on chemical safety at work, visit Health Canada’s chemical safety resources.
Safe Storage of Nitric Acid
Nitric acid must be stored in a cool, well-ventilated area away from combustible materials, organic solvents, and metals. It should be kept in appropriate acid-resistant containers with secure, tightly fitting lids.
Never store nitric acid near household chemicals or in areas accessible to children. In residential or laboratory settings, always follow local regulations for chemical storage and disposal.
Long-Term Health Effects of Nitric Acid Exposure
Repeated or severe exposure to nitric acid can have lasting effects on health. People who work in industries that use nitric acid regularly face a higher risk of chronic health problems if proper precautions are not taken.
Long-term inhalation of nitric acid fumes has been linked to chronic respiratory problems, including persistent cough, reduced lung capacity, and bronchitis. Some research also suggests repeated exposure may irritate the mucous membranes of the nose and throat over time.
Severe chemical burns from nitric acid can result in permanent scarring. In some cases, damaged tissue may require skin grafting or other surgical procedures. Eye injuries, if not treated promptly, can lead to permanent vision impairment or blindness.
For detailed information on the health effects of industrial chemicals, you can refer to resources from the World Health Organization (WHO), which provides international guidance on chemical hazard assessment.
When to See a Doctor
Any exposure to nitric acid — no matter how minor it seems — warrants medical attention. Do not wait to see if symptoms improve on their own, especially with eye or inhalation exposure.
For non-emergency situations — such as mild skin irritation after brief contact that was thoroughly rinsed — you can visit a walk-in clinic. Most Canadian cities and towns have walk-in clinics that can assess minor chemical burns and advise on wound care.
However, if exposure was significant — meaning prolonged skin contact, any eye contact, inhalation of fumes, or accidental ingestion — go to an emergency room immediately or call 911. Do not drive yourself if you are feeling unwell.
Your family doctor is also a good resource for follow-up care after an acid exposure. They can check for delayed symptoms, refer you to a specialist if needed, and help you understand your options under your provincial health plan. If you do not have a family doctor, a walk-in clinic or your provincial telehealth line (such as Ontario’s Telehealth Ontario at 1-866-797-0000 or BC’s HealthLink 811) can guide you.
As always, consult a qualified healthcare professional before making any decisions about your health. The information in this article is for general educational purposes only and is not a substitute for medical advice.
You can also find reliable general health information through Mayo Clinic’s chemical burn overview, which outlines treatment steps and when to seek emergency care.
Frequently Asked Questions
What does nitric acid do to the human body?
Nitric acid is a highly corrosive substance that reacts with skin, eyes, and tissue on contact, causing painful chemical burns. Exposure can also damage the lungs if fumes are inhaled. The yellow or orange staining it leaves on skin is a key sign of nitric acid contact.
Is nitric acid dangerous at home?
Nitric acid is not a common household chemical, but it can be found in some industrial cleaning products. If you ever encounter nitric acid outside of a professional setting, treat it as a serious hazard and keep it away from children. Always store and dispose of chemicals according to local Canadian safety regulations.
What should I do if nitric acid touches my skin?
If nitric acid touches your skin, remove any contaminated clothing and flush the area with large amounts of cool running water for at least 20 minutes. After rinsing, cover the area and go to a walk-in clinic or emergency room right away. Do not apply creams or home remedies before seeing a healthcare provider.
Can you smell nitric acid?
Yes, concentrated nitric acid has a strong, sharp, and suffocating odour. Smelling this odour in a confined space may mean you are already being exposed to harmful fumes. Leave the area immediately and get fresh air if you detect this smell in a workplace or laboratory setting.
What colour is nitric acid?
Pure nitric acid is colourless, but it often appears yellow or yellowish-brown due to dissolved nitrogen dioxide gas. When nitric acid contacts skin, it leaves a distinctive yellow or orange stain. This colour change is a reliable sign that the skin has been exposed to the acid.
Who should I call in Canada if someone swallows a chemical like nitric acid?
Call 911 immediately for any ingestion of nitric acid, as this is a life-threatening emergency. You should also contact your provincial Poison Control Centre — the national number is 1-844-764-7669. Do not try to make the person vomit, and keep them calm while waiting for emergency help to arrive.
Key Takeaways
Nitric acid (HNO3) is a powerful corrosive mineral acid used in industry and laboratories across Canada.
It can cause serious chemical burns to the skin, eyes, and internal organs upon contact or ingestion.
Inhaling nitric acid fumes is dangerous — symptoms of lung damage can appear hours after exposure.
First aid always begins with flushing the affected area with large amounts of water for at least 15 to 20 minutes.
Call 911 for serious exposures. For mild irritation, visit a walk-in clinic or call your provincial telehealth line.
Canadian workers handling nitric acid are protected by provincial occupational health and safety laws — know your rights.
Always consult a doctor or healthcare professional if you have been exposed to nitric acid, even if symptoms seem mild at first.
