Formaldehyde is a vital ingredient in many chemical and manufacturing processes. Unfortunately, like many useful materials, this colorless, flammable gas also presents a serious exposure hazard to people in industrial workplaces and, potentially, homes, buildings and other areas.

Formaldehyde has many uses and is widely found in chemical plants that produce resins used as a binder in the manufacturing of wood products such as plywood and particleboard. The strong-smelling material is also used in manufacturing paper products, leather goods and pharmaceuticals, and is used as a tissue preservative in certain medical facilities.

Normally present in both indoor and outdoor air at low levels — usually less than 0.03 parts per million (ppm) — formaldehyde can also be produced through combustion of organic fuels, including wood and wood products, coal, gasoline or diesel fuel. It can even be found in side stream smoke from tobacco products. It has been classified as a probable human carcinogen.

Exposure level thresholds

Exposure to formaldehyde, which primarily occurs through inhalation, depends on both the form of the material (solid, liquid or gas) as well as the concentration of formaldehyde present. Since most regulations require sampling to be taken from the employee’s breathing air zone, gaseous form of formaldehyde monitoring is typical.

California Code of Regulations, Title 8, Section 5217 requires employers to monitor formaldehyde if employee exposure to formaldehyde exceeds the 0.5 ppm action level or the 2 ppm STEL. Employers are then required to monitor for exposure and inform employees of monitoring results. Posting the results where employees have ready access to them constitutes compliance with the standard.

The current American Council of Governmental Industrial Hygienists (ACGIH) Threshold Limit Value (TLV) for formaldehyde indicates a ceiling level of 0.3 ppm. This means that the level of 0.3 ppm should not be exceeded at any time. OSHA indicates a TWA (8-hour time-weighted average) of 0.75 ppm, and a STEL (15-minute average Short-Term Exposure Limit) of 2 ppm. NIOSH limits are 0.16 ppm for the TWA, and ceiling of 0.1 ppm. Internationally, the World Health Organization exposure limit is 0.08 ppm for a 30-minute average.

Testing standards

EPA Method IP-6A has been one of the most widely used standards for measuring ambient levels of formaldehyde. With this method, formaldehyde vapors are collected on a sorbent material coated with 2,4-dinitrophenylhydrazine (DNPH), with the sorbent material then analyzed using high-performance liquid chromatography (HPLC) in a laboratory. NIOSH Method 5700 uses a similar method based on DNPH for measurement of formaldehyde.

NIOSH Method 3500 uses visible absorption spectrometry to analyze formaldehyde collected in sodium bisulfite solution and then, in a laboratory, reacted with chromotropic acid.

Detection methods

Both stationary and portable instruments are available, using several different detection methods. Traditional methods of detection have been through use of passive or active sampling methods such as reagent tubes and badges. Some of these devices are direct-reading, meaning that, at the end of a prescribed time period or sampling process a concentration can be determined by comparing a color change of the reagent to a chart or to a marking on the reagent tube.

Active sampling methods are also available, whereby a measured amount of air is drawn through a tube using a sampling pump at a controlled flow rate for a fixed period of time, or a measured number of squeezes or strokes of a manual device.

Other passive devices such as sorbent tubes or badges are also common.

More advanced methods of detection include direct-reading instruments available specifically for formaldehyde. With direct-reading instruments, indications of formaldehyde level can be determined at the time of the testing, as opposed to waiting for laboratory analysis. Direct-reading methods include the use of chemically impregnated tapes or tablets and electrochemical sensors.

For both chemical tapes and tablets and electrochemical sensors, the user should verify whether or not any interfering gases or vapors might be present in their environment. Because the selectivity of these methods varies depending on the manufacturer, and because of the need for detecting very low levels of formaldehyde, false positives can be an issue. Gases like acetone, ammonia, carbon dioxide and carbon monoxide can potentially cause a response with formaldehyde monitors.