The primary ways to reduce chemical hazards follow a ranked system called the hierarchy of controls: elimination, substitution, engineering controls, administrative controls, and personal protective equipment (PPE). These five strategies range from most to least effective, and the best workplaces layer several together rather than relying on just one.
The Hierarchy of Controls
OSHA and NIOSH both recommend following the hierarchy of controls when addressing chemical hazards. The logic is straightforward: it’s better to remove a danger entirely than to ask workers to protect themselves from it. The five levels, ranked from most to least effective, are:
- Elimination: Physically removing the hazardous chemical from the process
- Substitution: Replacing a dangerous chemical with a safer one
- Engineering controls: Using equipment or physical barriers to keep chemicals away from workers
- Administrative controls: Changing how, when, or how long people work around chemicals
- Personal protective equipment: Wearing gear that blocks chemical contact
Elimination, substitution, and engineering controls are considered more effective because they work without relying on human behavior. Administrative controls and PPE depend on people consistently following rules and wearing gear correctly, which makes them less reliable on their own.
Elimination and Substitution
Elimination means redesigning a process so the hazardous chemical is no longer needed at all. In the paper industry, for example, a newer bleaching technology uses a compound called a polyoxometalate that completely eliminates the need for chlorine dioxide, a hazardous chemical traditionally used to bleach wood pulp. The toxic chemical simply isn’t part of the process anymore, so no exposure can occur.
Substitution swaps a dangerous chemical for something less harmful. This might mean using a water-based cleaner instead of a solvent-based one, or switching to a lower-toxicity adhesive. In chemical manufacturing, reactive distillation methods can eliminate or significantly reduce the need for solvents compared to traditional production. The key principle is the same: if you can get the job done with something less dangerous, do it.
Engineering Controls
When you can’t get rid of the chemical entirely, engineering controls put a physical barrier or ventilation system between the chemical and the worker. Local exhaust ventilation is the primary method for controlling inhaled chemical exposures. These systems use a hood, ductwork, and a fan to capture airborne contaminants right where they’re released.
Chemical fume hoods are the most common engineering control in laboratories. When used properly, they minimize or eliminate exposure to hazardous vapors and also reduce the risk of injury from spills or reactions. Modern variable air volume (VAV) hoods adjust airflow automatically while maintaining safe velocity levels. Even the best fume hoods, though, are only certified to contain chemical leakage below 0.1 parts per million. For extremely hazardous substances, toxic gases, or explosive materials, a sealed glove box or isolation device offers better protection.
Ductless fume hoods are another option. These standalone units pull air through carbon or HEPA filters and release the cleaned air back into the room, which can work well when connecting to a building’s ductwork isn’t practical. Specialized hoods also exist for specific chemicals. Perchloric acid, for instance, requires a stainless steel hood equipped with water wash-down capabilities because it can deposit shock-sensitive crystals.
Administrative Controls
Administrative controls don’t remove the hazard. Instead, they reduce how much contact workers have with it. NIOSH defines these as work practices that reduce the duration, frequency, or intensity of exposure. Common examples include rotating workers through tasks so no single person spends a full shift around a chemical, limiting access to areas where chemicals are used, scheduling chemical-intensive work when fewer people are present, and requiring specific training before handling certain substances.
Proper labeling and communication fall into this category too. OSHA updated its Hazard Communication Standard in May 2024 to align with the seventh revision of the Globally Harmonized System (GHS) for chemical classification and labeling. This means standardized safety data sheets and labels with nine recognizable pictograms that identify specific dangers: a skull and crossbones for acute toxicity, a flame for flammable materials, a corrosion symbol for substances that burn skin or eyes, an exclamation mark for irritants, and others covering health hazards like carcinogens, explosives, oxidizers, pressurized gases, and environmental toxins. These labels give workers immediate visual information about what they’re handling.
Personal Protective Equipment
PPE is the last line of defense. It includes gloves, goggles, face shields, respirators, and chemical-resistant clothing. It ranks lowest in the hierarchy because it only works when worn correctly and consistently, and it can fail.
Choosing the right PPE matters more than most people realize. Chemical gloves, for example, aren’t universal. Each glove material resists different chemicals for different amounts of time. The critical measurement is breakthrough time: how long it takes a chemical to pass through the glove material and reach your skin. Once breakthrough occurs, the glove no longer provides adequate protection, even if it looks fine. The permeation rate measures how fast the chemical moves through the material at steady state. Selecting gloves means checking compatibility charts for the specific chemicals you’re working with, not just grabbing whatever is in the supply closet.
Storage, Containment, and Emergency Equipment
Proper chemical storage prevents hazards before they start. Incompatible chemicals need to be separated so they can’t react with each other if a container leaks. Secondary containment, such as trays, dikes, or double-walled cabinets, catches spills before they spread. EPA regulations require bulk storage installations to provide secondary containment capable of holding the entire volume of the largest single container, plus enough extra space to account for rainwater.
Emergency equipment is essential wherever corrosive or injurious chemicals are used. OSHA requires eyewash stations and emergency showers in areas where workers could be splashed. Under the ANSI Z358.1 standard, eyewash stations must be within 10 seconds of the hazard (roughly 55 feet), deliver water at 0.4 gallons per minute for a full 15 minutes, and supply tepid water between 60 and 100 degrees Fahrenheit. The water stream must hit between 33 and 53 inches from the floor and at least 6 inches from any wall or obstruction. These aren’t suggestions. They’re specific requirements designed so a person who just got a chemical splash in their eyes can reach help fast enough to prevent permanent damage.
Layering Multiple Controls
In practice, the most effective chemical safety programs combine several levels of the hierarchy. A lab might substitute a less toxic solvent (substitution), use it inside a fume hood (engineering control), limit the number of people who handle it (administrative control), and require splash goggles and chemical-resistant gloves for anyone who does (PPE). No single measure is foolproof, but stacking them creates redundancy. If one layer fails, the others still reduce exposure. The goal is always to push controls as high up the hierarchy as possible, relying on PPE only for the residual risk that better controls can’t fully address.