Substituting designated substances with those that are less hazardous is encouraged and often the best way of controlling exposures.  In situations where the designated substance is completely removed from the workplace, the regulation no longer applies.

The regulation requires that the control program provide for:

  • engineering controls
  • work practices
  • hygiene facilities and practices  

Another type of control is personal protective equipment, which is discussed in another chapter.

These controls will vary depending on the circumstances, but employers and workplace parties should ensure they not only comply with their obligations in O. Reg. 490/09 but any other applicable obligations under the OHSA.

Engineering controls

Other than substitution, the best method for controlling exposure to hazardous substances is engineering controls. Engineering controls include measures to reduce the release of the substance at the source or along the path of transmission and should be considered in the design of the workplace, equipment and processes.

There are four basic types of engineering controls:

An overview of these is discussed below.

Process control

It may be possible to modify the process in a way that reduces emissions and controls exposures to the substance. For example, using wet methods in grinding and drilling operations will reduce dust. Dipping or painting with a brush instead of spray painting will reduce the release of contaminants into the air.

Enclosure and isolation

Enclosing a process or equipment can be very effective in reducing the amount of a substance released into the workplace. Keeping the enclosed process or equipment under negative pressure by means of exhaust ventilation and the use of double mechanical seals on pumps and valves affords greater protection.

Isolation can separate workers from processes which are using a designated substance. For example, hazardous processes may be in areas of the plant that are physically or geographically separate from where many workers are present.

If high risk manual operations are unavoidable, glove boxes, remote control devices or robots may be used to minimize worker exposure. An alternative is to situate workstations in contaminant-free enclosures or booths, especially where automated processes are used.

Local exhaust ventilation

Local exhaust ventilation is one of the most effective means of controlling workplace exposures at the source of emission.

A local exhaust ventilation system has four main parts:

  • the hood, where contaminated air enters the ventilation system
  • ducts, which carry contaminated air away from its source
  • the air-cleaning device, which removes contaminants from air before it is discharged
  • the fan and motor, which draw air into the system and discharge it after cleaning

The design of these parts must be suitable for the process and substance being controlled.

General ventilation

General or dilution ventilation involves the use of large volumes of air to dilute the concentration of airborne contaminants. In the event of airborne exposures to designated substances, usually general ventilation alone does not offer adequate control and local exhaust ventilation is needed.

It is important that a general ventilation system include an adequate supply of replacement air* to prevent a negative pressure being created (Note: This situation occurs when the workplace air is allowed to leave and is not replaced), which can adversely affect the operation of exhaust fans and other equipment.

* Where applicable, see section 128 of O. Reg.851 – Industrial Establishments and section 20 of O. Reg. 67/93 Health Care and Residential Facilities.

Work practices

In addition to engineering controls, a control program must also provide for work practices to ensure workers are protected from exposure to a designated substance.  Work practices are to be set out in the control program and examples include the following:

Housekeeping

Good housekeeping procedures are especially important when a designated substance is released in a particulate form.  For example, dust on equipment and other surfaces can lead to exposures and should be kept to a minimum or eliminated.

Cleaning techniques should not contribute to the dispersal of dust and should be performed using wet sweeping, sweeping compounds or vacuum cleaners equipped with special filters or other devices to prevent dust from being re circulated into the air.  For example, a vacuum equipped with a HEPAfilter should be used for cleaning of surfaces contaminated with silica dust.

Equipment maintenance

Regular maintenance of equipment can help prevent leaks or emissions of a designated substance into the workplace.  Equipment provided by the employer, including that used for control practices such as ventilation systems or vacuum cleaners, must be maintained in good condition

Administrative controls

Administrative controls are work practices that can reduce a worker’s exposure to a contaminated environment. They may include:

  • scheduling maintenance, or other high exposure operations, at times when few workers are present
  • job-rotation schedules that limit the amount of time each individual worker is exposed to a designated substance
  • work-rest schedules that limit the duration of worker exposure to a designated substance

Hygiene facilities and practices

Hygiene facilities and practices can reduce the amount of a designated substance absorbed through the skin or ingested by a worker. They are especially important when the designated substance is released in a form that can accumulate on workers’ hands and other exposed skin, clothing and hair.

Important principles to remember when planning for effective hygiene facilities and practices include the following, some of which may also be required by the sector-specific regulations under the OHSA:

  • the routes of exposure to the designated substance and need for restrictions on eating and drinking in work areas
  • location of lunchrooms, rest areas and drinking fountains to minimize risk of contamination
  • stressing handwashing before eating, drinking or smoking and removing of outer protective clothing followed by cleaning hands and other exposed areas of the body before entering rest areas, lunchrooms and when leaving the workplace
  • where appropriate, hygiene facilities should be designed to prevent contamination of clean clothes by dirty clothes. Well-designed hygiene facilities customarily feature washing and showering areas located between “clean” and “dirty” changing areas
  • worker education programs should address the importance of good hygiene practices and the prevention of exposures

HEPA filter” means a high-efficiency particulate air filter that is at least 99.97 per cent efficient in removing particle s with a mean aerodynamic diameter of 0.3 micrometres from the air.