Oral ingestion of hydrocarbons often is associated with symptoms of mucous membrane irritation, vomiting, and central nervous system depression. Cyanosis, tachycardia, and tachypnea may appear as a result of aspiration, with subsequent development of chemical pneumonitis. Other clinical findings include albuminuria, hematuria, hepatic enzyme derangement, and cardiac arrhythmias. Doses as low as 10 ml orally have been reported to be potentially fatal, whereas some patients have survived the ingestion of 60 ml of petroleum distillates. A history of coughing or choking in association with vomiting strongly suggests aspiration and hydrocarbon pneumonia. Hydrocarbon pneumonia is an acute hemorrhagic necrotizing disease that can develop within 24 h after the ingestion. Pneumonia may require several weeks for complete resolution.

Symptoms of chemical (hydrocarbon) pneumonia may include:

- burning of the nose, eyes, lips, mouth, and throat

- dry cough

- wet cough producing clear, yellow, or green mucus

- cough producing blood or frothy pink matter

- nausea or abdominal pain

- chest pain

- shortness of breath

- painful breathing or pleuritis (an inflammation of the outside covering of the lungs)

- headache

- flu symptoms

Acute:

- Cough

- Difficulty Breathing

- Abnormal lung sounds (wet, gurgling sounding breaths)

- Chest pain, tightness or burning

Chronic:

- Persistent cough

- Shortness of breath

- Increased susceptibility to respiratory illness

Symptoms of chronic chemical pneumonitis may or may not be present, and can take months or years to develop to the point of noticeability.

Fire breather’s pneumonia usually presents with certain non-specific symptoms, and may vary significantly among individuals. The most common symptoms include:

- Cough

- Dyspnea (shortness of breath)

- Chest pain

- Fever

- Weakness

- Hemoptysis (coughing up blood)

Acute pneumonitis typically begins asymptomatic, with a worsening of symptoms over the course of hours or days. Following aspiration of fuel, there is often a period of latency from 8–24 hours before the symptoms occur. Patients may not recall a specific instance of aspiration. Severe cases may lead to acute respiratory distress syndrome (ARDS).

Hydrocarbon pneumonitis is a kind of chemical pneumonitis which occurs with oral ingestion of hydrocarbons and associated aspiration. It occurs prominently among children, accounting for many hospital admissions each year. Common hydrocarbons involved are mineral spirits, mineral seal oil (common in furniture polish), lamp oil, kerosene (paraffin), turpentine (pine oil), gasoline, and lighter fluid. Pneumatocele is a complication of hydrocarbon pneumonitis. In both childhood and adult pneumonitis, hydrocarbon aspiration occurs at the time of initial ingestion event or subsequently with vomiting. Low viscosity of an ingested hydrocarbon is considered a major factor promoting aspiration (presumably for mechanical reasons). Contrary to aspiration hydrocarbon pneumonitis, hydrocarbon (solvent) vapor inhalation manifests primarily in either central nervous system or cardiac effects.

Chemical pneumonitis is inflammation of the lung caused by aspirating or inhaling irritants. It is sometimes called a "chemical pneumonia", though it is not infectious. There are two general types of chemical pneumonitis: acute and chronic.

Irritants capable of causing chemical pneumonitis include vomitus, barium used in gastro-intestinal imaging, chlorine gas (among other pulmonary agents), ingested gasoline or other petroleum distillates, ingested or skin absorbed pesticides, gases from electroplating, smoke and others. It may also be caused by the use of inhalants.

Mendelson's syndrome is a type of chemical pneumonitis.

Mineral oil should not be given internally to young children, pets, or anyone with a cough, hiatus hernia, or nocturnal reflux, because it can cause complications such as lipoid pneumonia. Due to its low density, it is easily aspirated into the lungs, where it cannot be removed by the body. In children, if aspirated, the oil can work to prevent normal breathing, resulting in death of brain cells and permanent paralysis and/or retardation

Some symptoms and signs of Bagassosis include breathlessness, cough, haemoptysis, slight fever. Acute diffuse bronchiolitis may also occur. An xray may show mottling of lungs or a shadow.

Fire breather's pneumonia, also known as fire breather's lung or fire-eater's lung, is a distinct type of exogenous—that is, originating outside the body—lipoid pneumonia (chemical pneumonitis) that results from inhalation or aspiration of hydrocarbons of different types, such as lamp oil. Accidental inhalation of hydrocarbon fuels can occur during fire breathing, fire eating, or other fire performance, and may lead to pneumonitis.

Symptoms can vary significantly among individuals, ranging from asymptomatic to a severe, life-threatening disease. Onset usually occurs within hours, though symptoms may not appear for several days. Lipoid pneumonia is a rare condition, but is an occupational hazard of fire performers.

Patients with subacute HP gradually develop a productive cough, dyspnea, fatigue, anorexia, weight loss, and pleurisy. Symptoms are similar to the acute form of the disease, but are less severe and last longer. On chest radiographs, micronodular or reticular opacities are most prominent in mid-to-lower lung zones. Findings may be present in patients who have experienced repeated acute attacks.

The subacute, or intermittent, form produces more well-formed noncaseating granulomas, bronchiolitis with or without organizing pneumonia, and interstitial fibrosis.

It can be classified into acute interstitial pneumonitis, blood pneumonitis, lymphocytic interstitial pneumonitis, radiation pneumonitis, and uremic pneumonitis.

This disease is an inflammation of the alveoli in the lungs. Initial symptoms are breathlessness especially after sudden exertion or when exposed to temperature change and can be very similar to asthma, hyperventilation syndrome or pulmonary embolism. One of the defining characteristics of "bird fanciers lung" is that many medical tests will show a normal range of results and it will be identified by X-ray or CT scans showing physical changes to the lung structure (a ground glass appearance). If someone with BFL has been exposed to avian proteins they will see symptoms within 4–6 hours. Symptoms include chills, fever, breathlessness, non-productive cough and chest discomfort. In the chronic form there is usually anorexia, weight loss, extreme tiredness and progressive interstitial fibrosis which is the most disabling feature of the disease as this causes scarring on the lungs which reduces the lungs ability to move air in and out, and as a result sufferers have repeated chest infections and ultimately struggle to breathe. This condition is occasionally fatal.

The pneumonia presents as a foreign body reaction causing cough, dyspnoea, and often fever. Haemoptysis has also been reported.

The most common symptoms of acute interstitial pneumonitis are highly productive cough with expectoration of thick mucus, fever, and difficulties breathing. These often occur over a period of one to two weeks before medical attention is sought. The presence of fluid means the person experiences a feeling similar to 'drowning'. Difficulties breathing can quickly progress to an inability to breathe without support (respiratory failure).

Acute interstitial pneumonitis typically progresses rapidly, with hospitalization and mechanical ventilation often required only days to weeks after initial symptoms of cough, fever, and difficulties breathing develop.

In chronic HP, patients often lack a history of acute episodes. They have an insidious onset of cough, progressive dyspnea, fatigue, and weight loss. This is associated with partial to complete but gradual reversibility. Avoiding any further exposure is recommended. Clubbing is observed in 50% of patients. Tachypnea, respiratory distress, and inspiratory crackles over lower lung fields often are present.

On chest radiographs, progressive fibrotic changes with loss of lung volume particularly affect the upper lobes. Nodular or ground-glass opacities are not present. Features of emphysema are found on significant chest films and CT scans.

Chronic forms reveal additional findings of chronic interstitial inflammation and alveolar destruction (honeycombing) associated with dense fibrosis. Cholesterol clefts or asteroid bodies are present within or outside granulomas.

In addition, many patients have hypoxemia at rest, and all patients desaturate with exercise.

Signs and symptoms of flock worker's lung include rales (crackling noises caused by fluid in the lungs), dyspnea (shortness of breath), and coughing. Abnormalities seen on a computed tomography (CT) scan of the lungs can include ground glass opacity and reticular opacity. The typical histopathology in flock worker's lung is bronchiolocentric interstitial pneumonitis and lymphocytic bronchiolitis with lymphocytic hyperplasia. Occasionally, desquamative interstitial pneumonia and bronchiolitis obliterans organizing pneumonia can be seen.

Other symptoms described in flock workers include pleuritic chest pain and atypical chest pain. Most cases described have been chronic and progressive. Lung function in individuals with flock worker's lung is generally diminished, with both restrictive and obstructive defects found.

The gross appearance of a lipid pneumonia is that in which there is an ill-defined, pale yellow area on the lung. This yellow appearance explains the colloquial term "golden" pneumonia.

At the microscopic scale foamy macrophages and giant cells are seen in the airways, and the inflammatory response is visible in the parenchyma.

The signs and symptoms of PAP include shortness of breath, a cough, low grade fever, and weight loss.

The clinical course of PAP is unpredictable. Spontaneous remission is recognized, and some patients have stable symptoms. Death may occur due to the progression of PAP or of any underlying associated disease. Individuals with PAP are more vulnerable to lung infections such as bacterial pneumonia, mycobacterium avium-intracellulare infection, or a fungal infection.

Bagassosis has been shown to be due to a thermophilic actinomycetes for which the name thermoactinomycetes sacchari was suggested.

Farmer’s lung reactions can be categorized as acute and chronic reactions. Acute and chronic reactions have the same symptoms but for chronic reactions, the symptoms are much more severe. Farmer’s lung symptoms include:

- Chills

- Fever

- Irritating/harassing cough

- Runny nose

- Sputum streaked with blood

- Tightness of the chest

- Difficult and laboured breathing

- Crackling of breath

- Muscular pain

- Depression

These symptoms develop between four and eight hours after exposure to the antigens. In acute attacks, the symptoms mimic pneumonia or flu. In chronic attacks, there is a possibility of the victim going into shock and dying from the attack.

Classification can be complex, and the combined efforts of clinicians, radiologists, and pathologists can help in the generation of a more specific diagnosis.

Idiopathic interstitial pneumonia can be subclassified based on histologic appearance into the following patterns:

Usual interstitial pneumonia is the most common type.

Pneumonitis or pulmonitis is an inflammation of lung tissue due to factors other than microorganisms. Those can be radiation therapy of the chest , exposure to medications used during chemo-therapy, the inhalation of debris (ie animal dander), of food particles during vomiting, herbicides or fluorocarbons and some systemic diseases.

It is distinguished from pneumonia on the basis of causation as well as its manifestation since pneumonia can be described as pneumonitis combined with consolidation and exudation of lung tissue due to infection with microorganism.

People with infectious pneumonia often have a productive cough, fever accompanied by shaking chills, shortness of breath, sharp or stabbing chest pain during deep breaths, and an increased rate of breathing. In the elderly, confusion may be the most prominent sign.

The typical signs and symptoms in children under five are fever, cough, and fast or difficult breathing. Fever is not very specific, as it occurs in many other common illnesses, may be absent in those with severe disease, malnutrition or in the elderly. In addition, a cough is frequently absent in children less than 2 months old. More severe signs and symptoms in children may include blue-tinged skin, unwillingness to drink, convulsions, ongoing vomiting, extremes of temperature, or a decreased level of consciousness.

Bacterial and viral cases of pneumonia usually present with similar symptoms. Some causes are associated with classic, but non-specific, clinical characteristics. Pneumonia caused by "Legionella" may occur with abdominal pain, diarrhea, or confusion, while pneumonia caused by "Streptococcus pneumoniae" is associated with rusty colored sputum, and pneumonia caused by "Klebsiella" may have bloody sputum often described as "currant jelly". Bloody sputum (known as hemoptysis) may also occur with tuberculosis, Gram-negative pneumonia, and lung abscesses as well as more commonly with acute bronchitis. "Mycoplasma" pneumonia may occur in association with swelling of the lymph nodes in the neck, joint pain, or a middle ear infection. Viral pneumonia presents more commonly with wheezing than does bacterial pneumonia. Pneumonia was historically divided into "typical" and "atypical" based on the belief that the presentation predicted the underlying cause. However, evidence has not supported this distinction, thus it is no longer emphasized.

The typical symptoms of UIP are progressive shortness of breath and cough for a period of months. In some patients, UIP is diagnosed only when a more acute disease supervenes and brings the patient to medical attention.

Acute interstitial pneumonitis (also known as acute interstitial pneumonia or Hamman–Rich syndrome) is a rare, severe lung disease that usually affects otherwise healthy individuals. There is no known cause or cure.

Acute interstitial pneumonitis is often categorized as both an interstitial lung disease and a form of acute respiratory distress syndrome (ARDS) but it is distinguished from the "chronic" forms of interstitial pneumonia such as idiopathic pulmonary fibrosis.

Aspiration pneumonia is often caused by a defective swallowing mechanism, often due to a neurological disease or as the result of an injury that directly impairs swallowing or interferes with consciousness. Examples of the former are stroke, Parkinson's disease, and multiple sclerosis, and examples of the latter are some types of dementia, seizures, intoxication, and general anaesthesia. For many types of surgical operations, patients are therefore instructed to take nothing by mouth (nil per os, abbreviated as NPO) for at least four hours before surgery.

The location is often gravity dependent, and depends on the patient position. Generally, the right middle and lower lung lobes are the most common sites affected, due to the larger caliber and more vertical orientation of the right mainstem bronchus. Patients who aspirate while standing can have bilateral lower lung lobe infiltrates. The right upper lobe is a common area of consolidation in alcoholics who aspirate in the prone position.